Kines 101 Exam 2 (practice exams, quizzes, clicker questions)
Just before a baseball is struck by a bat, its velocity is +40.0 m/s (positive means directed away from the pitcher). Just after being hit, the ball's velocity is -60.0 m/s (negative means directed toward the pitcher). If the impact with the bat takes 200 ms, what is the magnitude of the average acceleration of the ball during the impact? (Note that you are just being asked for the magnitude of the acceleration here. This means that all you should be looking for is the size of the acceleration and not its direction. For example, the magnitude of an acceleration that is -1000 m/s is 1000 m/s, because we can ignore the negative sign that just indicates direction and not magnitude.) - 200 m/s/s - 400 m/s/s - 500 m/s/s - none of the above answers is correct
- 500 m/s/s The change in velocity is -100 m/s because the ball goes from +40 m/s to -60 m/s. This happens in 0.2 s, so the average acceleration is -100/0.2 = -500 m/s/s. The magnitude (size) of the acceleration is 500 m/s/s. What if you had been asked what the direction of the average acceleration was? You'd say that the acceleration was directed toward the pitcher. You could say this because the acceleration comes out negative and you're told negative is toward the pitcher. Or, you could reason that the velocity changes in a way that makes the ball head more toward the pitcher than away from the pitcher.
Just before the left foot touches the ground (when only the right foot is touching the ground) during the walking of a 67 kg subject, the vertical component of the ground reaction force (GRF) applied to the right foot is measured to be 640 N. What is the vertical component of the acceleration of the subject's center of mass? Give your answer to the nearest 0.01 m/s/s. (Hint: Draw a "free-body diagram", or FBD) - 0.26 m/s/s, directed down - 9.55 m/s/s, directed down - 9.81 m/s/s, directed down - none of these answers is correct
0.26 m/s/s, directed down Remember that only vertical forces cause vertical accelerations. Let's think about what the vertical forces are. Your FBD should show two vertical forces, the given vertical GRF G (an upward force) and the weight W (a downward force). Use Newton's Second Law (Fnet = ma). The net force is G - W, the GRF minus the weight, so G - mg = ma With G = 640 N and m = 67 kg, a = -0.26 m/s/s. Negative means down here because the weight, a downward force, was chosen to be negative earlier.
Which of these could be the length of a Penn State student's foot? - 2.7 m - 0.27 m - 27 mm -0.027 km
0.27 m
A man begins walking in a straight line by starting from rest (velocity of zero). By the time he has been walking for 3.0 s, his forward velocity is 1.5 m/s. What is the magnitude of the man's average acceleration during this time? - 0.0 m/s/s - 0.4 m/s/s - 0.5 m/s/s - none of the above answers is correct
0.5 m/s/s Average acceleration is found by dividing change in velocity by change in time. A = 1.5 / 3.0 = 0.50 m/s/s.
A patient in hand therapy completes a reaching task in which his fingertip moves 32 cm along a straight path in 400 ms. What is the fingertip's average velocity during the movement? (hint: All the answers below are in m/s, so it would be a good idea to convert centimeters (cm) to meters and milliseconds (ms) to seconds before computing velocity) - 0.8 m/s - 1.25 m/s - 1.5 m/s - none of the above answers is correct
0.8 m/s To find average velocity we divide displacement D by time T. To find velocity in m/s, we'll express displacement in m and time in seconds before we take the quotient. D = 32 cm = 0.32 m, and T = 400 ms = 0.400 s. Dividing, we get Vavg = 0.32 / 0.400 = 0.8 m/s.
During a bench press while a barbell (weight = 1000 N) is moving downward, an 1200 N upward force is applied with the hands to the barbell to slow it down. If no other forces are being applied to the barbell at this time, what is the acceleration of the barbell? (Round your answer to the nearest 0.01 m/s2) - 0.98 m/s2 up - 1.96 m/s2 up - 9.81 m/s2 down - 11.77 m/s2 up
1.96 m/s2, up From the previous question, we know that the net external force on the barbell is 200 N up. To find the acceleration, we'll use the 2nd Law: F_net = ma. We're not given the mass of the barbell, but we do know its weight (1000 N). Since W = mg, we can find the mass as m = 1000 / 9.81 = 101.9 kg. Using a = F / m = 200 / 101.9 gives a = 1.96 m/s/s. The net force is up, so the acceleration is up.
At one instant during a training run, a 70 kg runner's instantaneous velocity is 5.5 m/s in the forward direction. What is the runner's kinetic energy at this instant? Give your answer to the nearest 1 J. - 385 J - 687 J - 1059 J - None of the above answers is correct
1059 J Kinetic energy depends on velocity and is equal to KE = 0.5 m v2, so for this runner, KE = 0.5 * 70 * (5.5)2 = 1059 J
A 10 kg plate slips off a barbell and falls to the floor, striking the floor with a velocity of 5.6 m/s, directed straight down. If the plate started with an initial velocity of zero, how far did it fall before hitting the floor? You can neglect the effects of air resistance here. Round your answer to the nearest centimeter. (Hint: You can use conservation of energy to solve this problem) - 87 cm - 112 cm - 160 cm - 213 cm
112 cm (Quiz 3 question 19) Very similar to the diver problem we did in class. We're assuming wind resistance does no work on the diver, so energy is conserved and the gain in KE will be equal to the loss in GPE: EnergyTOP = EnergyBOTTOM 0.5 m vTOP2 + m g hTOP = 0.5 m vBOTTOM2 + m g hBOTTOM We can say vTOP = 0 and hBOTTOM = 0, so (canceling m on both sides) g hTOP = 0.5 vBOTTOM2 With vBOTTOM = 5.6 m/s and g = 9.81 m/s2, we get hTOP = 1.60 m = 160 cm
A 93 kg football player is hit by a tackler who drives him to the right with a force of 1175 N. If the feet of the player who was hit are off the ground so we can neglect ground reaction force, what is the player's horizontal acceleration? Round your answer to the nearest 0.1 m/s/s. - 12.6 m/s/s - 18.0 m/s/s - 21.7 m/s/s - none of the above are correct
12.6 m/s/s Use F=ma, so 1175=93a and a=12.6m/s/s
The frictional (tangential) force applied to the foot of a runner is 300 N, directed posteriorly. At the same time an upward normal force of 1490 N acts on the same foot. What is the magnitude of the resultant (vector sum) of these two forces acting on the foot? Give your answer to the nearest 1 N. - 1490 N - 1503 N - 1520 N - None of the above answers are correct
1520 N To solve this problem, we need to add the two forces. Because one is horizontal and one is vertical, we have to add them like vectors. This is done by making a right triangle with legs equal to 300 and 1490 and then we use Pythagorean Theorem to solve for hypotenuse, which is the vector sum (or "resultant").
A 67 kg diver falls through a vertical distance of 3 m. How much does his gravitational potential energy change during the fall? Give your answer to the nearest 1 J. - 0 J - 657 J - 1972 J - None of the above answers is correct
1972 J The gravitational potential energy of a body depends on its height and is given by GPE = mgh. If we take h=0 at the end and h=3 m at the start then the change in GPE = 67 x 9.81 x 3 = 1972 J.
What is the velocity of an 80 kg skydiver who is falling with 16,000 J of translational kinetic energy? Give your answer to the nearest 1 m/s. - 10 m/s - 20 m/s - 200 m/s - 400 m/s
20 m/s KE = 0.5 m v^2 so 16000 = 0.5 * 80 * v^2 v^2 = 16000/40 = 400 v = 20 m/s
During a bench press while a barbell (weight = 1000 N) is moving downward, an 1200 N upward force is applied with the hands to the barbell to slow it down. If no other forces are being applied to the barbell at this time, what is the net (total) external force applied to the barbell? - 200 N, down - 200 N, up - 1200 N, up - 2200 N, up
200 N up these two forces tend to cancel each other out leaving a net force of 200 N up
A golf ball is hit off the tee with a velocity of 50 m/s at an angle that is 30 degrees above the horizontal. What is the magnitude of the vertical component of the ball's velocity? Give your answer to the nearest 0.1 m/s. - 14.8 m/s - 20.0 m/s - 25.0 m/s - None of the above answers is correct
25.0 m/s To solve this, we have to "resolve" (break up) the velocity vector into its horizontal and vertical components. To do this, you draw a right triangle and make the original vector the hypotenuse, then find the legs of the triangle. If you draw the correct right triangle you'll have sin(30) = Vy/50.
At one instant during walking, a 90 kg subject's horizontal acceleration is measured to be 0.3 m/s/s, directed posteriorly. What is the net horizontal ground reaction force applied to the feet (i.e., the sum of the foot forces) at this time? Give your answer to the nearest 1 N. - 27 N, directed posteriorly - 36 N, directed posteriorly - 45 N, directed posteriorly - None of these answers is correct
27 N, directed posteriorly Remember that only horizontal forces cause horizontal accelerations. Contact with the ground is the only source of horizontal force. Use the 2nd Law: Fnet = ma. Choosing posterior to be negative, Fnet = (90)(-0.3) = -27 N The negative sign means that the 27 N is directed posteriorly. What if we had chosen posterior to be positive? This would make the given acceleration positive: Fnet = (90)(0.3) = +27 N The positive sign means that the 27 N is directed posteriorly (same as before) because this time positive means posterior.
Zdeno Chára of the Boston Bruins holds the world record for the fastest slap shot, at 48.64 m/s. If, while the hockey puck is in flight, we assume that the puck has a constant velocity of 48.64 m/s along a straight line, how far will the puck travel in 750 ms? You may assume that the puck's average velocity during this time is equal to the given constant velocity. - 36.48 m - 54.12 m - 64.85 m - none of the above answers is correct
36.48 m When the velocity is constant, the value of the constant velocity is identical to the average velocity. Referring to the formula for average velocity., Vavg = (x2-x1)/T. Here we are given Vavg (48.64 m/s) and T (750 ms, or 0.75 s) and need to find x2-x1. The answer is 36.48 m.
When a man holds two dumbbells with arms outstretched as shown in Example 6.6 (see notes), the adducting moment applied to each arm by gravity is 120 Nm. If the deltoid muscle is the only muscle holding up the arm by providing an opposing abduction moment of 120 Nm, and the deltoid's moment arm is 3 cm, what is the force generated by each deltoid muscle? - 3200 N - 3600 N - 4000 N - None of the above answers are correct
4000 N Moment of force is given by M = F d, and we are told that M = 120 N m and d = 3 cm = 0.03 m, so F = 120 / 0.03 = 4000 N.
Find the body mass in SI units for a patient who weighs 143 lbs. Round to the nearest kg. - 65 kg - 82 kg - 398 kg - none of the above answers is correct
65 kg An object that has a mass of 1 kg weighs 2.2 pounds. To convert pounds to kg, multiply by a form of 1 (fraction equal to one) that makes pounds cancel and leaves you with kg. The form of 1 you'll use here is (1 kg /2.2 lbs). 143 lbs * (1 kg /2.2 lbs) = 65 kg.
A pole vaulter (body mass = 70 kg) has just cleared the bar and is falling to the mat below. What is the pole vaulter's weight? Give your answer to the nearest 0.1 newtons. - 0.0 N - 686.7 N - 781.0 N - None of the above answers is correct
686.7 N
The frictional (tangential) force applied to the foot of a runner is 300 N, directed posteriorly. At the same time an upward normal force of 1490 N acts on the same foot. What is the angle formed between the horizontal and the vector that is the resultant (sum) of these two forces acting on the foot? Give your answer to the nearest 0.1 degrees. - 11.4 degrees - 45.0 degrees -78.6 degrees - 89.0 degrees
78.6 degrees To find the angles within a right triangle, we'll use the inverse tangent (atan) function. In this case, the angle with horizontal is equal to atan(1490/300) = 78.6 deg. Choice 1 is angle with vertical.
Which of the following could be the weight of an adult human male? - 80,000 kN - 8,000 N - 800 N - 80 N
800 N 800 N is about 180 lbs. It's not necessary to memorize this conversion, but 1 lb. is 4.45 N, and you should have an idea of your own weight in newtons - this should help you to get this answer. All the other answers are too far off to be people: A garbage truck might weigh 80,000 N. A small car might weigh 8,000 N. A suitcase full of clothes might weigh 80 N.
A man rides a bicycle ergometer for 30 minutes and during this time his feet do 200,000 J of work on the pedals. Which of the following values could be the metabolic energy expended by the man (that is, the amount of energy derived from all metabolic sources) during this time? - 50,000 J - 100,000 J - 200,000 J - 800,000 J
800,000 J We are not perfectly efficient when exercising; if we were then every bit of energy derived from food would have been delivered to the pedals (200,000 J). The first two choices are impossible because energy has come from nowhere to drive the pedals. The last choice (800,000 J) is best because it reflects an efficiency of 0.25, which is typical -- see notes.
A hockey puck with mass 112 g is contacted by the blade of a hockey stick, which applies a rightward force of 900 N to the puck. What force is applied to the blade of the stick by the puck? Round your answer to the nearest 1 N. - 0 N, no force is applied to the stick by the puck - 900 N, directed to the left - 900 N, directed to the right - 1099 N, directed down
900 N directed to the left Two bodies in contact exert equal and opposite forces on one another (Newton's third law of motion)
A girl doing "jumping jacks" is moving her arms and legs in the transverse plane. - True - False
False
A single muscle fiber is made up of many muscle fascicles. - True - False
False
An example of an eccentricmuscle contraction occurs when a boy's knee extends and his quadriceps muscles shorten as he kicks a soccer ball. - True - False
False
Anatomy is the study of forces and motions arising within the musculoskeletal system. - True - False
False
Andreas Vesalius made some of the first photographic images of humans and animals in motion - True - False
False
Henry Gray was among the first to perform experiments in which human muscles were electrically stimulated - True - False
False
Moment of force may be expressed in units of newtons (N) - True - False
False
Muscle force is generated when crossbridges are formed between adjacent molecules of adenosine triphosphate (ATP). - True - False
False
The human body could be separated into left and right halves by a transverse plane. - True - False
False
The kilogram is a unit of gravitational force - True - False
False
There are one thousand centimeters in a meter - True - False
False
Trabecular bone (also called cancellous bone) is the dense, solid material that makes up very small bones. - True - False
False
refer to a diver who leaps from a 10 m high platform and falls to the water below. Neglect air resistance (and all other forces except for gravity) in answering these questions. As the diver falls he loses kinetic energy. - True - False
False
refer to a hockey puck that is gliding to the right with constant velocity across a frictionless ice surface. You may neglect the effects of air resistance. The acceleration of the puck is directed to the right - True - False
False
refer to a hockey puck that is gliding to the right with constant velocity across a frictionless ice surface. You may neglect the effects of air resistance. The normal contact force acting on the puck is zero - True - False
False
refer to a hockey puck that is gliding to the right with constant velocity across a frictionless ice surface. You may neglect the effects of air resistance. There is a net force acting on the puck that is directed to the right. - True - False
False
refer to a man performing a bench press in which a barbell is pushed up and away from his chest. When the barbell is moving upward it is losing gravitational potential energy. - True - False
False
refer to a man who begins by holding a 50 N dumbbell at his side and then raises it sideways (abducting at the shoulder) while keeping his arm straight. After he has raised the dumbbell, he holds it in a static position with his arm horizontal for a few seconds before lowering it back to his side. When the dumbbell is held in the raised static position, it is primarily held there by the moment generated by the deltoid muscle, an abductor of the shoulder. The force generated by the deltoid muscle will be approximately equal to 50 N. - True - False
False
refer to a man who stands with his arms outstretched, then brings his arms into his body and folds them across his chest. The mass of the man's body is greater with the arms outstretched - True - False
False
refer to a patient with Parkinson's disease who starts from rest and walks the length of a 24 m hallway in 30 s. During this time the patient never stops walking forward. The patient's acceleration must be directed forward throughout the 30 s. - True - False
False
refer to a patient with Parkinson's disease who starts from rest and walks the length of a 24 m hallway in 30 s. During this time the patient never stops walking forward. The patient's average walking velocity over the 24 m cannot be determined from the information given. - True - False
False
refer to anthropometric measures A stadiometeris a device primarily used to determine percent body fat - True - False
False
refer to anthropometric measures Anyone whose body mass index (BMI) places them in the "overweight" category is at elevated risk for diseases such as heart disease and diabetes - True - False
False
refer to measurements of leg length made in a large sample of 20-year-old female subjects. The mean leg length for this sample is found to be 83 cm and the sample standard deviation is found to be 3 cm About as many subjects would be expected to have leg lengths that fall in the 6-cm interval between 80 cm and 86 cm as would be expected to have leg lengths that fall in the 6-cm interval between86 cm and 92 cm - True - False
False
refer to normal, healthy human walking. You may assume that the gait cycle begins and ends with a right foot contact (heelstrike). The time period between 60% and 100% of the gait cycle corresponds to the right leg stance phase - True - False
False
refer to normal, healthy human walking. You may assume that the gait cycle begins and ends with a right foot contact (heelstrike). When a person walks forward the horizontal component of the ground reaction force acting on the right foot is always directed in the anterior direction when the right foot is on the ground. - True - False
False
refer to the arm pictured below. The elbow is flexed to 90° and the force generated by the biceps muscle is 700 N. The moment arm of the biceps force about the elbow is 5 cm. The only other force acting is a downward force F acting on the hand. The arm is in static equilibrium. The magnitude of the force F is at least 700 N. - True - False
False
refer to the arm pictured below. The elbow is flexed to 90° and the force generated by the biceps muscle is 700 N. The moment arm of the biceps force about the elbow is 5 cm. The only other force acting is a downward force F acting on the hand. The arm is in static equilibrium. The magnitude of the moment of the 700 N biceps force about the elbow is 140 N m. - True - False
False
refer to the energetic cost of locomotion (Em, also called "cost of transport", with units ofcal kg-1 m-1), and the rate of energy consumption during walking (EW, with units of cal kg-1 min-1). Normal walking is most energetically efficient when Em is highest - True - False
False
refer to the energetic cost of locomotion (also called "cost of transport"), which is sometimes designated Em and which is measured in calories per kilogram of body mass per meter traveled (cal kg-1 m-1). The energetic efficiency of normal walking (as indicated by energetic cost) is best when humans walk at the slowest possible speed. - True - False
False
refer to the moment of inertia of the whole body of a diver who leaps from a 10 m high platform Once the diver leaves the platform, her moment of inertia cannot change - True - False
False
refer to the moment of inertia of the whole body of a diver who leaps from a 10 m high platform The moment of inertia of the diver at a specified instant during the dive depends on how fast her body is rotating. - True - False
False
refer to the normal, healthy human gait cycle, which begins and ends with a right foot contact (heelstrike). The gait cycle has exactly one double-support phase that lasts 10% of the gait cycle. - True - False
False
refer to the race run by Jamaican Usain Bolt when he broke the world record in 2009. Please note that the 100 m dash is a race that begins from rest and is run in a straight line. Bolt's acceleration must have been in the forward direction throughout the entire race. - True - False
False
refer to the race run by Jamaican Usain Bolt when he broke the world record in 2009. Please note that the 100 m dash is a race that begins from rest and is run in a straight line. Bolt's average velocity for the entire race is obtained by dividing his instantaneous velocity at the finish line by two. - True - False
False
refer to the vertical ground reaction force (GRF) applied to one foot during normal human walking on typical surfaces. The anterior-posterior GRF that acts on one foot is always directed anteriorly during the stance phase, pushing the body forward. - True - False
False
refer to the vertical ground reaction force (GRF) applied to one foot during normal human walking on typical surfaces. The vertical GRF peaks at about 2.2 times the body weight during normal walking - True - False
False
A body in mechanical equilibrium cannot have any forces acting upon it. - True - False
False "Equilibrium" implies that the forces acting on the body must add up to zero, but it doesn't mean that no forces can be acting. Two forces that cancel one another out could be acting and the net force would be zero. Follows from 2nd Law -> Fnet = ma. Example: a person standing still is in equilibrium but gravitational and ground contact forces act on the person.
Questions 5-7 refer to a pole vaulter executing a pole vault, starting with the run up and ending just before contact with the landing mat. True or false: The pole vaulter has no kinetic energy until he leaves the ground. - True - False
False Kinetic energy is associated with motion. In an equation, KE = 0.5 m v2. Because the pole vaulter is moving (running) before he leaves the ground, he has velocity and therefore KE before he leaves the ground.
Mass is measured using Newtons - True - False
False Mass is measured in kilograms (kg) and force is measured in newtons (N)
A runner's forward velocity may be expressed in meters per second squared - True - False
False Velocity is change in position (measured in m) divided by the time it takes to change position (measured in s), so the units of velocity will be m/s. You would measure how fast velocity changes (also called acceleration) using meters per second squared. Another way to think of this is that acceleration is an expression of how many meters per second your velocity changes by every second. This is meters per second per second, or meters per second squared.
If the net force acting on a body is zero, then the net moment acting on the body must also be zero. - True - False
False We find the total moment acting on a body by adding up the moments due to each force acting on the body. We don't do this by finding the net force first. Here's why: Two equal and opposite forces cancel each other out, yielding zero net force, but if those forces are not collinear (acting along the same line) there will be a net moment. See lecture notes for a picture.
A runner completing the 100 m dash in typical fashion (running in a straight line; no running start; runs through the finish line) must have an instantaneous velocity at the finish line that is twice his average velocity for the race. - True - False
False Average velocity is total displacement (change in position) divided by total time, in this case 100 m divided by the race time. It has no relation to the instantaneous velocity, which is the velocity at any one point in time. Resist the temptation to find an average velocity by taking the average of two velocities.
When you shake your head as if to indicate "no" in answer to a yes-no question, you are rotating your skull in the sagittal plane. - True - False
False ; this is a transverse plane motion
Guillaume Duchenne made one of the first motion pictures when he analyzed the movements of a horse's hooves. - True - False
False; it was Edward Muybridge
How much work is done against gravity as a 50 kg barbell is raised from the floor to a height of 2 m above the floor, if we know that the barbell begins and ends with zero velocity? Give your answer to the nearest 1 J. - 25 J - 100 J - 200 J - None of the above answers are correct
None of the above answers are correct There is an equivalence between work and energy. This means that if I do 100 J of work on a body, its energy increases by 100 J, as long as no force other than gravity (such as friction) also acts on the body. The barbell's kinetic energy is the same at the end as it is at the beginning (zero), so the work done on the barbell must be equal to the change in gravitational potential energy (GPE). Work = mghAFTER - mghBEFORE = 50 * 9.81 * 2 - 0 = 981 J You could also get this answer by noting that the average upward force F applied to barbell is equal to weight of barbell F = 50 * 9.81. This upward force will be a little greater than this at the beginning when the weight accelerates upward and a little less at the end when it slows down. Work = F d, so = (50 * 9.81) * 2 = 981 J
A muscle that generates force actively while shortening is said to be contracting concentrically. - True - False
True
A myofibril consists of a number of sarcomeres connected end-to-end - True - False
True
Angular velocity may be expressed using units of degrees per second (° s^-1) - True - False
True
Biomechanics is the study of forces and motions as applied to biological systems. - True - False
True
Body weight may be expressed in units of newtons (N) - True - False
True
Diaphysisis the term for the tubular shaft of a long bone that is made of cortical (compact) bone. - True - False
True
Eadward Muybridge was among the first to photograph humans and animals in motion for biomechanical analysis. - True - False
True
Giovanni Borelli made detailed drawings illustrating actions of levers within the musculoskeletal system - True - False
True
Gray's Anatomy is an influential anatomy test first published in 1858 and still in print today - True - False
True
Henry Gray published a classic anatomy text in 1858 - True - False
True
If you start with your right arm hanging down at your side and then perform an abduction of the right shoulder, your right arm will be confined to the frontal plane. - True - False
True
In an "concentric" muscle contraction, the muscle shortens. - True - False
True
Interest in the human form on the part of artists led to renewed interest in the study of anatomy during the Renaissance. - True - False
True
Muscle force is generated when structures called crossbridges form, rotate, and release. - True - False
True
Newton's Second Law implies that when the same net force is applied separately to two bodies that have the same mass, then the accelerations of the two bodies will be the same. - True - False
True
One challenge faced by those who study biomechanics is that human bodies cannot be tested or measured in the same ways that machines can be tested or measured. - True - False
True
Origin is name for one of the places where tendon attaches to bone. - True - False
True
The "origin" of a muscle-tendon unit refers to the location where its proximal tendon attaches to bone. - True - False
True
The contractile proteins in muscle are called actin and myosin. - True - False
True
The elbow is surrounded by a capsule containing lubricating fluid - True - False
True
The hip is a synovial joint - True - False
True
The hip is a synovial joint. - True - False
True
The joints in your hand and fingers that allow you to make a fist are synovial joints - True - False
True
The right elbow is proximal to the right wrist - True - False
True
The study of anatomy was furthered during the Renaissance by artists who sought more realistic depictions of the human form. - True - False
True
When you are standing up, your right ankle is "inferior to" your right knee. - True - False
True
Your right ear and your left ear could both be properly described as being "lateral to" your brain. - True - False
True
refer to a baseball that has been thrown by a pitcher and is midway between the pitcher's mound and home plate (i.e., in midair and not in contact with any player or bat). You may neglect the effects of air resistance. The horizontal component of the acceleration of the baseball is zero (if we neglect air resistance) - True - False
True
refer to a baseball that has been thrown by a pitcher and is midway between the pitcher's mound and home plate (i.e., in midair and not in contact with any player or bat). You may neglect the effects of air resistance. The only force acting on the ball (if we neglect air resistance) is its weight - True - False
True
refer to a baseball that has been thrown by a pitcher and is midway between the pitcher's mound and home plate (i.e., in midair and not in contact with any player or bat). You may neglect the effects of air resistance. The weight of the baseball depends (in part) on its mass - True - False
True
refer to a diver who leaps from a 10 m high platform and falls to the water below. Neglect air resistance (and all other forces except for gravity) in answering these questions. It is proper to say that gravity "does positive work" on the diver as he falls - True - False
True
refer to a diver who leaps from a 10 m high platform and falls to the water below. Neglect air resistance (and all other forces except for gravity) in answering these questions. The sum of the diver's kinetic energy and gravitational potential energy is constant as he falls - True - False
True
refer to a man performing a bench press in which a barbell is pushed up and away from his chest. It is proper to say that the upward forces applied by the hands to the barbell "do work against gravity" as the barbell is raised from its lowest position to its highest position. - True - False
True
refer to a man performing a bench press in which a barbell is pushed up and away from his chest. When the barbell is moving upward it has kinetic energy. - True - False
True
refer to a man who begins by holding a 50 N dumbbell at his side and then raises it sideways (abducting at the shoulder) while keeping his arm straight. After he has raised the dumbbell, he holds it in a static position with his arm horizontal for a few seconds before lowering it back to his side. The moment of the gravitational force acting on the dumbbell about the axis of rotation through the shoulder increases as the dumbbell is lifted away from the body. - True - False
True
refer to a man who stands with his arms outstretched, then brings his arms into his body and folds them across his chest. The man's body is more resistant to rotation about a superior-inferior axis when the arms are outstretched - True - False
True
refer to a man who stands with his arms outstretched, then brings his arms into his body and folds them across his chest. The moment of inertia of the man's body about a superior-inferior axis is greater with the arms outstretched - True - False
True
refer to a patient with Parkinson's disease who starts from rest and walks the length of a 24 m hallway in 30 s. During this time the patient never stops walking forward. The patient's instantaneous velocity at the 24 m mark cannot be determined from the information given - True - False
True
refer to anthropometric measures. A man and a woman who are both 5' 9" tall and who both weigh 160 lbs. will have the same body mass index. - True - False
True
refer to anthropometric measures. Many human size variables are normally distributed about their mean values - True - False
True
refer to measurements of leg length made in a large sample of 20-year-old female subjects. The mean leg length for this sample is found to be 83 cm and the sample standard deviation is found to be 3 cm The value the sample standard deviation would be expected to be larger than 3 cm if the sample were of female subjects aged 8 years to 20 years rather than being limited to 20-year-olds - True - False
True
refer to normal, healthy human walking. You may assume that the gait cycle begins and ends with a right foot contact (heelstrike). At the time corresponding to 5% of the gait cycle, both feet are on the ground - True - False
True
refer to the energetic cost of locomotion (Em, also called "cost of transport", with units ofcal kg-1 m-1), and the rate of energy consumption during walking (EW, with units of cal kg-1 min-1). EW takes on its lowest values at the lowest walking speeds - True - False
True
refer to the energetic cost of locomotion (also called "cost of transport"), which is sometimes designated Em and which is measured in calories per kilogram of body mass per meter traveled (cal kg-1 m-1). Having a high energetic cost indicates energetic inefficiency and is equivalent to getting poor "mileage" - True - False
True
refer to the moment of inertia of the whole body of a diver who leaps from a 10 m high platform Moment of inertia is an indication of a body's resistance to rotation. - True - False
True
refer to the motion of a wheelchair along a straight path As the wheelchair rolls forward and slows to a stop, the wheelchair has an acceleration that is directed backward. - True - False
True
refer to the motion of a wheelchair along a straight path The acceleration of the wheelchair and the net force applied to it must be in the same direction - True - False
True
refer to the motion of a wheelchair along a straight path When the velocity of the wheelchair is constant, its acceleration is zero - True - False
True
refer to the normal, healthy human gait cycle, which begins and ends with a right foot contact (heelstrike). The left foot is in the air for approximately 40% of the gait cycle - True - False
True
refer to the normal, healthy human gait cycle, which begins and ends with a right foot contact (heelstrike). The right stance phase lasts approximately 60% of the gait cycle. - True - False
True
refer to the race run by Jamaican Usain Bolt when he broke the world record in 2009. Please note that the 100 m dash is a race that begins from rest and is run in a straight line. Bolt's average acceleration over his first few steps out of the starting blocks was in the forward direction. - True - False
True
refer to the vertical ground reaction force (GRF) applied to one foot during normal human walking on typical surfaces. The graph of the vertical GRF acting on one foot plotted against time has a characteristic "double-bump" pattern during normal walking. - True - False
True
A body in mechanical equilibrium could be moving. - True - False
True "Equilibrium" means no acceleration (and therefore no net force). A body can have a nonzero velocity but have zero acceleration. As an example, think of a hockey puck gliding across a frictionless ice surface with a constant velocity.
When the pole is bent after the vaulter leaves the ground, the pole is storing elastic potential energy. - True - False
True A pole doesn't look like a spring but it behaves like one when it is bent and snaps back to its original shape. The energy associated with the deformation of a spring, or anything that behaves like a spring by snapping back to its undeformed position, is called elastic potential energy. For this class it's not important to know an equation for EPE, just that when materials are bent, stretched, or compressed and return to their original positions, they store and release EPE.
The gravitational potential energy of the vaulter is greatest when the pole vaulter reaches his peak height in the air. - True - False
True Gravitational potential energy depends on the mass of the body and its height above some reference height (such as the ground). As an equation it is GPE = mgh. GPE would be greatest at the top, when h is greatest as the vaulter clears the bar.
A dumbbell is raised during a biceps curl. The upper arm is vertical and the elbow is flexed to 90 degrees. The motion is performed slowly so you can assume that the angular acceleration of the forearm is zero. You can neglect the weight of the forearm. True or false: The weight of the dumbbell held in the hand will be less than the force generated by the biceps muscle at this time. - True - False
True It's tempting to say that the muscle force should be larger because the dumbbell is rising, but this ignores everything we know about rotational mechanics. Both forces are acting to cause rotation at the elbow - the muscle force has a moment that is in the elbow flexion direction and the weight does the opposite by tending to make the elbow extend. The arm is moving slowly, so you're told to assume zero angular acceleration (a good assumption for a slow biceps curl) so the moments of the two forces will be equal. In an equation, we would have FB * dB - W * dW = 0 The negative sign on one of these moments accounts for the fact that these moments cause opposite rotations at the elbow. The moment arm of the weight of the dumbbell about the elbow (dW) is huge (around 30 cm) compared to the moment arm of the biceps force about the elbow (dB, about 5 cm), so the biceps force FB will be much larger than the weight W. There is an example like this in the lecture notes.
Moment of force is reported using units of newton meters (N m). - True - False
True Moment of force is computed as the magnitude of a force multiplied by the perpendicular distance between the force's line of action and some point about which the moment is taken. The units for moment of force (or just "moment") are thus newton meters (N m).
A body could have a net force acting on it to the right while the body's velocity is directed to the left. - True - False
True The net force and the acceleration vectors must be in the same direction, but net force and velocity can be in opposite directions. For example, as you catch a ball that is dropped into your hand, the ball may move down as your hand applies an upward force to it that is greater than the ball's weight, slowing it down.
When you apply a forward-directed force to a baseball in order to throw it, the baseball exerts a backward force upon your hand. - True - False
True This is a straightforward application of the 3rd Law. Any time two bodies are touching each other, the forces exerted on each body by the other are equal and opposite to each other.
For a runner completing the 100 m dash in typical fashion, the instantaneous acceleration could be zero one second before the runner finishes the race. - True - False
True Zero acceleration signifies a constant velocity, and it's possible that the runner's forward velocity is not changing late in the race. It's also possible that the velocity is decreasing, which would be a backward acceleration (or a negative acceleration if we say that forward means positive). Be careful about confusing acceleration (how fast velocity is changing) with velocity. A runner can have a zero acceleration without having zero velocity.
Muscle contraction is produced by attachments formed between the proteins actin and myosin. - True - False
True Muscle force is produced when crossbridges form between actin and myosin, then rotate to produce translation between the sliding filament proteins.
A 65 kg gymnast holds a static "iron cross" position on the rings for 3.0 s. What is the sum of all the external forces (the net force) applied to the gymnast's body during this time (rounded to the nearest 1 N) a. 0 N b. 195 N c. 638 N d. None of these is correct
a. 0 N
A 45 kg gymnast is in equilibrium at one point during her balance beam routine. What is the sum of all the external forces (the net force) applied to the gymnast's body at this time (rounded to the nearest 0.1 N)? a. 0.0 N b. 9.8 N c. 441.5 N d. none of these is correct
a. 0.0 N
For the same set of ground reaction forces and body mass described in Question #49, what is the vertical acceleration of the patient's body (rounded to the nearest 0.01 m s-2) and its direction? a. 1.22 m s^-2 up b. 9.81 m s^-2 down c. 11.03 m s^-2 up d. none of these is correct
a. 1.22 m s^-2 up
For the same set of ground reaction forces and body mass described in Question #49, what is the magnitude of the horizontal acceleration of the patient's body (rounded to the nearest 0.01 m s-2)? a. 1.28 m s^-2 b. 2.33 m s^-2 c. 9.81 m s^-2 d. none of these is correct
a. 1.28 m s^-2
If I am walking at a speed of 84 m/min, what is my walking speed when it is expressed in m/s? a. 1.4 m/s b. 1.5 m/s c. 1.6 m/s d. None of these is correct
a. 1.4 m/s
If the pole vaulter in Question #55 is 3.0 m above the ground, what is the gravitational potential energy of his body relative to the ground at this instant (rounded to the nearest 5 J) a. 2060 J b. 2770 J c. 4005 J d. body weight
a. 2060 J
Which of the following could be the average foot length for the people in this room? a. 240 mm b. 2.4 cm c. 0.024 m d. 0.0024 km
a. 240 mm
Which of the following could be the average forearm length for the people in this room? a. 25 cm b. 2.5 m c. 25 mm d. 0.025 km
a. 25 cm
A baseball player running at 5.4 m/s slides into second base, coming to a stop in 900 ms. What is the magnitude of his average acceleration during the slide (rounded to the nearest 0.1 m/s2)? a. 6.0 m/s2 b. 9.8 m/s2 c. 48.6 m/s2 d. None of these is correct
a. 6.0 m/s2
refer to the same figure. If the moment of inertia of the lower leg and foot about the knee is 0.3 kg m2, and no other forces produce moments about the knee at this time, what is the magnitude of the angular acceleration of the lower leg and foot (rounded to the nearest 0.1 rad/s2)? a. 19.1 rad/s2 b. 20.4 rad/s2 c. 21.0 rad/s2 d. None of these is correct
b. 20.4 rad/s2
The athlete pictured above trains by dragging a weighted sled (m = 20 kg) across the ground. In doing so, he pulls with a force of 320 N at an angle that is 27° above the horizontal. What is the horizontal component of this pulling force (rounded to the nearest 1 N)? a. 196 N b. 285 N c. 320 N d. None of these is correct
b. 285 N
The vertical ground reaction force applied to the right foot of a 68 kg patient is 750 N, directed up, and the horizontal ground reaction force applied to the same foot is 87 N, directed posteriorly. At this time, the right foot is the only one touching the ground. What is magnitude of the resultant (vector sum) of these two forces (rounded to the nearest 1 N)? a. 663 N b. 755 N c. 837 N d. None of these is correct
b. 755 N
A man who weighs 822 N has a body mass (rounded to the nearest 0.1 kg) that is equal to a. 80.6 kg b. 83.8 kg c. 98.1 kg d. none of these is correct
b. 83.8 kg
For the diver in the previous question, which of these quantities is decreasing as he falls? a. kinetic energy b. gravitational PE c. elastic PE d. body weight
b. gravitational PE
Which is greatest? a. height in meters of a high jump bar being cleared by a high jumper b. mass in kg of a professional basketball player c. length in centimeters of an adult human femur
b. mass in kg of a professional basketball player
A 75 kg basketball player lands from a jump, striking the ground with a downward velocity of 4.0 m/s and quickly coming to rest. What is the direction of the player's average vertical acceleration during the time that he is coming to rest on the ground (i.e., after his feet touch the ground but before he stops moving)? a. downward b. upward c. acceleration is zero d. cannot be determined
b. upward
A 72 kg diver jumps off of a high cliff and 2.0 s later is travelling straight down with a velocity of 17.0 m/s. What is the translational kinetic energy of the diver at this instant (rounded to the nearest 100 J)? a. 1200 J b. 7200 J c. 10400 J d. none of these is correct
c. 10400 J
What is the weight of the sled described in Question #49 (rounded to the nearest 1 N)? a. 20 N b. 124 N c. 196 N d. None of these is correct
c. 196 N
A basketball player performing a drill starts from rest at one point on the gym floor then sprints forward and 4 s after he starts he stops at a point 20 m away from where he started. What is the magnitude of his average velocity (rounded to the nearest 0.1 m/s)? a. 0.0 m/s b. 4.0m/s c. 5.0 m/s d. none of these is correct
c. 5.0 m/s
Please refer to figure above, which shows the leg of a physical therapy patient performing a knee extension with no load applied other than the 51 N weight of the lower leg and foot (considered as a single body segment). The line of action of this weight passes 12 cm in front of the knee at the instant shown. Find the magnitude of the moment of the 51 N weight about the knee (rounded to the nearest 0.1 N m). a. 2.2 N m b. 4.3 N m c. 6.1 N m d. None of these is correct
c. 6.1 N m
A runner running forward at 6 m/s begins her "kick" at the end of the race and accelerates forward at a constant 1.8 m s-2 for 2 s. What is her velocity at the end of the 2 s acceleration period (rounded to the nearest 0.1 m/s)? a. 3 m/s b. 7.8 m/s c. 9.6 m/s d. none of these is correct
c. 9.6 m/s
A runner sprints in a straight line for 8.0 s and his average velocity is found to be 6.0 m/s. What is the distance that he sprinted (rounded to the nearest 0.1 m)? a. 8.0 m b. 24.0 m c. 56.0 m d. None of these is correct
d. None of these is correct
A runner begins an 800 m race from rest and her speed at the finish line is 9.6 m/s. What was her average speed for the entire race? a. 0.0 m/s b. 2.8 m/s c. 9.6 m/s d. cannot be determined from the information given
d. cannot be determined from the information given
A 70 kg pole vaulter has just cleared the bar and is falling back to the ground with a downward velocity of 13 m/s. What is the translational kinetic energy of his body at this instant (rounded to the nearest 5 J)? a. 350 J b. 910 J c. 4675 J d. None of these is correct
d. none of these is correct
For the same set of ground reaction forces described in Question #49, what is the angle formed between the resultant force vector and a vertical line (rounded to the nearest 0.1°)? a. 0.0 degrees b. 11.6 degrees c. 78.4 degrees d. none of these is correct
d. none of these is correct
A hockey puck with mass 112 g is contacted by the blade of a hockey stick, which applies a rightward force of 600 N to the puck. If this force is the only horizontal force applied to the puck, find the puck's horizontal acceleration. Round your answer to the nearest 1 m/s/s. - 10 m/s/s, to the right - 101 m/s/s, to the right - 8036 m/s/s, to the right - none of the above answers are correct
none of the above answers are correct Use Newton's Second Law, F = ma, which relates force and acceleration. Only one horizontal force acts, so F = 600 N. The mass is 112 g, but we need to express this in kg if acceleration is to come out in m/s/s: 0.112 kg. Solving, we get 5357 m/s/s.
A 112 g hockey puck glides across a frictionless ice surface with no horizontal forces acting on it. If the puck's velocity is 22.5 m/s to the right at t = 0 s, what will the puck's horizontal velocity be at t = 225 ms? Round your answer to the nearest 0.1 m/s. - 0.0 m/s - 10.0 m/s, to the right - 25.0 m/s to the right - none of the answers are correct
none of the answers are correct With no forces applied to it, the puck remains in uniform motion. That is, its velocity remains constant (Newton's First Law of Motion) and the velocity will be 22.5 m/s until a horizontal force acts to speed it up or slow it down.