PET4312 Applied Biomechanics Final
The maximum limiting friction that can be generated between the bag and the cart is 50 N. You need to slide the bag to the side of the cart. If you apply 50 N 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
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
Poisson's ratio refers to
the ratio of strain in the axial direction to strain in the transverse direction for each different type of material
A load that produces twisting of a body around its longitudinal axis is called a:
torsion load
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 may be increased by
widening the base of support in the direction of an oncoming force
The horizontal velocity of Serena's tennis serve is measured as 112 mi/hr (50 m/s). Horizontally, the ball travels 25 m 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?
0.50s
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
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 10m/s 4s into the race. She holds this speed for 4s and then gradually slows down until she crosses the finish line 10 s after she started the race. What is Ariel's average velocity for the whole race?
10m/s
George runs the football 15 yards straight downfield then 5 yards to the right before he is tackled. What was George's resultant displacement in yards?
15.8 yards
You are attempting to lift 100lb on the knee extension machine. The moment arm of the weight about the knee joint is 35 cm and the knee is flexed to 30°. What torque is created by the weight about the knee joint? Use the picture below as your reference for 30° knee flexion.
156Nm
A high jumper with a body weight of 820 N exerts average vertical force of 1640 N down on the floor for 0.75 s. The average vertical force exerted on the jumper by the floor is:
1640N
What class lever is used when you nod your head yes?
1st class
A 100 kg shot-putter pushes forward and upward on a 4 kg shot with a force of 1000 N. This force acts at an angle of 60° above horizontal. How much of this 1000 N force acts in the forward direction?
500N
A 90 kg weightlifter exerts a 1000 N force upward against a 50 kg barbell. How large is the net vertical force acting on the barbell?
510N
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
As the velocity of a concentric muscle action increases (such as throwing a ball), the maximum force a muscle can produce increase - 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
Choking up on a baseball bat will increase the angular velocity of the bat.
False
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 do to improve his ability to rotate the socket wrench?
Hold the socket wrench at the opposite end from the axis
When performing a vertical jump for maximal height, muscle spindles and Golgi tendon organs play a significant role 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
Torque is:
all answers are correct - the compression and distraction effects of a force - the product of force and moment arm - the tendency of a force to cause rotation
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
Please match the following movements with their corresponding plane. - knee flexion - shoulder abduction - hip rotation
knee flexion: sagittal/anteroposterior shoulder abduction: frontal/lateral/coronal hip rotation: transverse/horizontal
The research on the tension-length relationship of muscles indicates that a muscle is capable of generating maximal force when the muscle is
slightly longer than resting length
You have a 6lb bat. You also have a 3lb bat and tape and additional 3lb to the end of the bat furthest from the handle. Which bat has more inertia when you swing it?
the 3lb bat with the 3lb weight attached due to the location of the concentration of weight
The study of the forces that cause of tend to cause motion is called
kinetics
Please match the following activity descriptions with their corresponding concept within Newton's laws. - Pushing back on the starting blocks in track - Landing on a soft floor mat during a jump - Must be overcome to push a stationary file cabinet across the floor - A rubber ball making contact with the ground when dropped - Leaning away from a punch as the boxing glove hits your face - Trying to not overrun a base - Follow through of a throw
- Pushing back on the starting blocks in track: reaction - Landing on a soft floor mat during a jump: impulse - Must be overcome to push a stationary file cabinet across the floor: inertia - A rubber ball making contact with the ground when dropped: reaction - Leaning away from a punch as the boxing glove hits your face: impulse - Trying to not overrun a base: inertia - Follow through of a throw: impulse
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 10m/s 4s into the race. She holds this speed for 4s and then gradually slows down until she crosses the finish line 10 s after she started the race. What is Ariel's average acceleration during the first 4s into the race?
2.5m/s^2
George runs the football 15 yards straight downfield then 5 yards to the right before he is tackled. What was George's distance traveled in yards?
20 yards
A weightlifter 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
An 80 kg volleyball player lands from a jump and tries to stop her forward motion. The normal contact force exerted by the floor on her shoes is 2000 N. The friction force exerted by the floor on her shoes is 600 N acting backward on the player. What is the resultant ground reaction force exerted by the floor on the volleyball player's shoes?
2088N
What class lever is used when you lower your forearm down to the ground (lower the weight) during a bicep curl?
2nd class
The coefficient of dynamic friction between the grass and a 200 kg football blocking sled is 0.20. If a 100 kg football player only pushes horizontally against the sled, how large must the horizontal force be to keep the sled moving at constant velocity?
392N
How much force must be generated by the supraspinatus muscle to hold a 10lb dumbbell straight out of a 90° abduction position? The dumbbell is 30cm from the glenohumeral joint. The supraspinatus muscle insertion is 1.5cm from the glenohumeral joint. Use the picture below as a reference for 90° abduction postion.
900N
The coefficient of static friction between the sole of an athletic shoe and the basketball court floor is 0.67. Bill wears these shoes when he plays basketball. If Bill exerts a normal contact force of 1400N when he pushes off the floor to run down the court, how large is the friction force exerted by his shoes on the floor?
938N
With the previous knee extension question, the moment arm of the knee extensor muscles is 5cm. How much force must be produced by these muscles to lift the 100lb weight?
>3120N
You are coaching 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 do 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
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 fastest midflight?
Dive 2
Identify the true statement. - Decreasing the magnitude of a force acting on a surface area increases the amount of stress acting on the surface. - Increasing the magnitude of a force acting on a surface area increases the amount of stress acting on the surface. - Both statements are true. - Neither statement is true.
Increasing the magnitude of a force acting on a surface area increases the amount of stress acting on the surface.
Identify the true statement. - Both statements are true. - Increasing the surface area over which a force is distributed decreases the amount of stress acting on the surface. - Neither statement is true. - Decreasing the surface area over which a force is distributed decreases the amount of stress acting on the surface.
Increasing the surface area over which a force is distributed decreases the amount of stress acting on the surface.
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?
Lowered his jump height by raising his center of gravity
The principle of conservation of momentum restates
Newton's first law
The statement "a rotating body will maintain a state of constant angular motion unless acted on by an external torque" refers to
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
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
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
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 a sprinter uses starting blocks to enhance running performance, which of Newton's laws is best represented by the interaction of the sprinter's feet and the blocks as they push off?
action-reaction
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 60 m away. The ball's horizontal velocity is 30 m/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 5 m/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 plate first, the base runner or the baseball?
baserunner; takes 1 second to reach home plate
For a rotating object, such as a bicycle wheel, the acceleration direction 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
If you are holding a 6lb weight in your hand 35cm from your elbow joint and your biceps brachii is generating a 30lb upward force at its attachment 6cm from the axis at 30° of elbow flexion, what will happen to the weight and why?
drop the weight because overall the weight has a greater torque than the torque of the bicpes muscle
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
If a bag has a mass of 25 kg, how much force must you apply vertically to lift it off of a baggage cart?
greater than 245 N
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
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
Which quantity is the same in space as on the earth?
mass
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
When a you stretch your hamstrings and they assume a new "normal" lengthened position upon release, it is called
plastic
Which of the following joint types is the 1st carpometacarpal joint?
saddle/sellar
