APK4220C Study guide
The maximum limiting friction that cane be generated between the bag and the car is 50N. You need to slide the bag to the side of the cart. If you apply 50N horizontally on the bag.
the bag will remain motionless
In golf, the longest club is the driver and the shortest club is the pitching wedge. With which club would it be easier to hit the ball farther if both clubs are swung with the same angular velocity?
the driver due to its longer swing radius and faster linear velocity
During angular motion, what is the relationship between the length of the moment arm and the torque created (when the force used is constant)?
the longer the moment arm, the greater the torque
To determine the length of a moment arm, you would measure
the perpendicular distance from the axis of rotation to the force's line of action
Torque is:
the product of force and moment arm the tendency of a force to cause rotation the compression and distraction effects of a force
Why do we lean to the right when we hold a heavy suitcase in our left hand?
we are shifting our center of gravity back to the right and over our base of support
Stability against an oncoming force may be increased by
widening the base of support in the direction of an oncoming force
If a runner completes a 400-meter sprint around a 400 m track in 50 seconds, what is the runner's displacement with respect to the starting position?
0m
The coefficient of dynamic friction between the grass and a 300kg football blocking a sled is 0.35. If a 100kg football player only pushes horizontally against the sled, how large must the horizontal force be to keep the sled moving at constant velocity? F=ma / F=uR
1030N
The coefficient of static friction between the sole of an athletic shoe and the basketball court floor is 0.80. Bill wears these shoes when he plays basketball. If Bill exerts a normal contact force of 1420N when he pushes off the floor to run down the court, how large is the friction force exerted by his shoes on the floor? Possible formulas: F-u,R F-ma
1136N
A high jumper with a body mass of 140lb exerts an average vertical force of 1240N down on the floor for 0.5s. The average vertical force exerted on the jumper by the floor is:
1240N
What class lever is used when you nod your head yes?
1st class
George runs the football 41 yards straight downfield then 6 yards to the right before he is tackled. What was George's distance traveled in yards?
47 yards
A 90kg weightlifter exerts a 1500N force upwards against a 75kg barbell. How large is the net vertical force acting on the barbell?
764N
A weightlifter is attempting a biceps curl with a 45lb barbell. The moment arm of the barbell about the elbow joint is 40cm. What is the torque created by the barbell about the elbow joint?
80Nm
Choking up on a baseball bat and shortening its length will increase the angular velocity of the bat.
False
Identify the true statement.
Friction is affected by the size of the contact area of the object's in contact with each other
Jarrod is trying to change his flat tire, but the lug nut on the wheel is stuck and he is having trouble generating force to turn the socket wrench. What can Jarrod to to improve his ability to rotate the socket wrench?
Hold the socket wrench at the apposite end from the axis
John jumps up to block a shot in basketball. Just before he is off the ground, John raises both hands over his head. How did this action affect his jump height?
Increased his jump height by lowering this center of gravity I guess
A ball is projected into the air with a vertical velocity of 20m/s and horizontal velocity of 22m/s upon release. What is the balls vertical velocity at peak height?
Om/s
When you sit in your applied biomechanics class for 90 minutes, your intervertebral discs undergo prolonged compression but expand outwardly in proportion to the amount of compression they receive. This concept is known as:
Poisson's ratio
The research on the tension-length of muscles indicates that a muscle is capable of generating maximal force when the muscle is
slightly longer than resting length
The horizontal velocity of Serena's tennis serve is measured as 100m/s. Horizontally, the ball trave's 20m before reaching her opponent. If the ball didn't slow down when it bounced or because of air resistance, how long would it take to reach her opponent? Possible formulas: v=d/t F=ma
0.20s
Aweightlifter is attempting a biceps curl with a 45lb barbell. The moment arm of the barbell about the elbow joint is 40cm. The moment arm of the elbow flexor muscles is 4cm. How much force must be produced by these muscles to hold the 45lb barbell in static equilibrium?
2000N
A 60kg volleyball players lands from a jump and tries to stop her forward motion. The normal contact force exerted by the floor on her shoes is 2600N. The friction force exerted by the floor on he shoes is 800N acting backward on the player. What is the ground reaction force exerted by the floor on the volleyball player's shoes?
2720N
Ariel is running a 100m dash. When the start pistol fires, she leaves the starting block and continues to speed up until she reaches her top speed of 11m/s 3s into the race. She holds this speed for 5s and then gradually slows down until she crosses the finish line 11s after she started the race. What is Ariel's average acceleration during the first 3s into the race? Possible formulas: a=(vr-v)/t F=ma
3.67m/s2
What class lever is used when you raise your forearm up (lift the weight) during a bicep curl?
3rd class
George runs the football 41 yards straight downfield then 6 yards to the right before he is tackled. What was George's resultant displacement in yards?
41 yards
Ariel is running a 100m dash. When the start pistol fires, she leaves the starting block and continues to speed up until she reaches her top speed of 11m/s 3s into the race. She holds this speed for Ss and then gradually slows down until she crosses the finish line 11s after she started the race. What is Ariel's average velocity for the whole race? Possible formulas: v-d/t a-v/L
9.09m/s
A 100kg shot-putter pushes forward and upward on a 6kg shot with a force of 1200N. This force acts at an angle of 50° above horizontal. How much of this 1200N force acts in the forward direction?
919N
You are coaching a Little League baseball team. One of your players is having a hard time hitting the ball. He does a good job of choosing which pitches to swing at, but he keeps missing because his bat doesn't get around fast enough. What would you suggest that he to so that he can swing the bat around in time to contact the ball?
Choke up on the bat
See picture below. Mary performs three different dives and rotates through the same number of revolutions in the same amount of time in all three dives. In all the dives, Mary's positions at takeoff and just before water entry are identical layout positions. In dive 1, she is in a layout position midflight. In dive 2, she is in a tuck position midflight. In dive 3, she is in a pike position midflight. In which dive will Mary be rotating the slowest midflight?
Dive 1 in a layout position
Mary performs three different dives and rotates through the same number of revolutions in the same amount of time in all three dives. In all the dives, Mary's positions at takeoff and just before water entry are identical layout positions. In dive 1, she is in a layout position midflight. In dive 2, she is in a tuck position midflight. in dive 3, she is in a pike position midflight. In which dive will Mary be rotating the fastest midflight?
Dive 2 in tuck position
If you increase the time during which a constant force is applied to an object, what effect does this have on the impulse given to the object?
It increases the impulse
The study of the forces that cause of tend to cause motion is called
Kinetics
The concept that explains how a spinning baseball changes direction, or the lift force generated by spin, is called:
Magnus effect
Which quantity is the same in space as on the earth?
Mass
The statement "a rotating body will maintain a state of constant angular motion unless acted on by an external torque" can be applied to a merry-go-round that is in constant motion. Which of Newton's laws applies to this concept?
Newton's first law
A ball being held by someone running will continue to move in the same direction and with the same speed until the runner causes a change in motion of the ball. This best exemplifies
Newton's first law of motion
What is the relationship between torque and angular acceleration?
The greater the torque acting at the axis of rotation, the greater the angular acceleration of a given body
A load that produces twisting of a body around its longitudinal axis is called a
Torsion load
As a projectile is thrown into the air, its horizontal velocity decreases on the way up to Om/s at the top but increases on the way down at a rate of 9.81 m/s.
True
It is possible for a pole-vaulter to successfully clear a crossbar without having his or her center of gravity pass above it?
True
The moment arm distance for a muscle force changes throughout a joint's range of motion.
True
When performing a vertical jump for maximal height, muscle spindles and Golgi tendon organs play a significant role in explosiveness, Why does jumping following a quick squat allow for greater height than jumping after holding a squat for a few seconds?
When going into a quick squat, muscle spindles are recruited and their response is muscle contraction
If you fracture your femur, you will be told by your medical provider to start to weight bear as soon as the fracture site closes because of what guiding principle?
Wolff's law
The force that acts parallel to an object in contact with a surface and may result in the formation of blisters is called
a shear force
When performing a biceps curl, the biceps brachii is the _______ while the triceps brachii is the _______.
agonist, antagonist
The left fielder throws the baseball home from 60m away. the balls horizontal velocity is 30m/s, and its vertical velocity is sufficient to keep it in the air until it reaches the catcher at home plate. At the same time, a base runner is running toward home plate. His velocity is 5m/s and he is 5 m from home plate. If the base runner's velocity stays constant and air resistance isn't a factor, which will arrive at home base first, the base runner or the baseball and why?
baserunner; takes 1 second to reach home plate
The force that always acts vertically upward in a fluid or gas is called
buoyancy
For a rotating object, such as a bicycle wheel, the acceleration directed toward the center of rotation is called
centripetal acceleration
What class lever is being used in the raising portion of a standing heel raise activity?
class 2
Bone is strongest in resisting
compressive stress
When articular cartilage is exposed to constant compressive stress, the strain in the cartilage will increase gradually with time. This concept is called
creep
Kinematics is the branch of mechanics that:
describes the pattern of motion
While walking and then running at a constant speed with the same ball, you want to release each ball in time for it to land in a target. In order for the ball that you run with to hit the target, when would you have to release the ball you run with relative to the release of the ball you walk with?
earlier than the ball you walk with
When going down into a squat, the quadriceps muscles control the movement at the knee via ________ contraction.
eccentric
When a you stretch your hamstrings and they return to their original pre-stretch length upon release, it is called
elastic
Muscles have the unique properties of extensibility, contractility, elasticity, and
excitability
As the velocity of a concentric contraction increases (such as throwing a ball), the maximum force a muscle can produce increases in other words, the faster your arm can move to throw a ball, the more force the arm muscles can exert on the ball.
false
If a bag has a mass of 40kg, how much force must you apply vertically to lift it off a baggage cart?
greater than 392N
While running at a constant speed with 2 balls of different weights, you drop the balls at the same time while running past a target. Both balls continue to move in the same direction as the runner upon release as they descend to the ground. Assuming air resistance is negligible, why do the balls hit the ground at the same time?
law of universal gravitation
What type of bone is the fibula?
long
In the average female compared to the average male, the center of gravity of the average female is located
lower than in the average male
While running at a constant speed with 2 balls of different weights, you drop the balls at the same time while running past a target. Both balls continue to move in the same direction as the runner upon release as they descend to the ground. Why do the balls keep moving in the same direction as the runner upon release?
momentum
During the throwing lab, the ball that was thrown with a wind up but no follow through went further than the ball that had no wind up but only a follow through because it had:
more impulse
When a you stretch your hamstrings and they then assume a new "normal" lengthened position upon release, it is called
plastic
