Deck 2: Kinetics of Linear Motion

Question 1

Which answer is true regarding the definition of weight:

A) Weight is a measure of the number of atoms or molecules within an object.
B) Weight is a measure of density that is measured in kilograms.
C) Weight refers to the quantity of air that is present within an object.
D) Weight is a measure of force exerted on the object (due to gravity) measured in Newtons.
E) Weight will always be greater on the moon than on Earth.

Answer 1

D
Explanation: Weight is a measure of force exerted on the object (due to gravity) measured in Newtons.

Question 2

What would be the weight of a 10kg object on Earth at sea-level in England?

A) 98.1N
B) 89.1N
C) 16.2N
D) 26.1N
E) 10kg

Answer 2

A
Explanation: As the acceleration due to gravity on Earth is 9.81m/s², the weight (mass x acceleration due to gravity) of a 10kg object on Earth would be 98.1N

Question 3

When a person is running they apply a force to the ground through their foot strike that occurs in the transverse, frontal and sagittal planes. What is the name of the resultant force that allows us to propel ourselves forward (or in the direction of the run)?

A) Braking Force
B) Vertical Force
C) Gravitational Force
D) Impact Force
E) Ground Reaction Force

Answer 3

E
Explanation: The resultant force that occurs during running and is derived from the composition of the forces that are applied across three planes is referred to as the Ground Reaction Force.

Question 4

The inertia of an object is directly related to its mass.

Question 5

The force that is exerted by a muscle to pull on a tendon and bone to flex a joint (e.g. when bringing the forearm closer to the upper arm during a bicep curl movement) would be classed as an 'attractive force'.

Question 6

All forces will produce or alter motion.

Question 7

Name three things that may affect the forces that are applied to the ground through foot strike during running (and therefore influencing the ground reaction force).

Question 8

Two parallel forces are acting on an object vertically upwards and one opposing force is acting on the same object vertically downwards. The forces are as follows.
35N upwards
63N upwards
78N downwards
Calculate the resultant force (magnitude and direction).

Question 9

The acceleration due to the pull from the mass of the Earth for all objects close to the Earth's surface, (gravity) is said to be what?

A) 8.91 m/s²
B) 98.1 m/s²
C) 9.81 m/s²
D) 89.1 m/s²
E) 1.98 m/s²

Question 10

When two objects of obviously different masses (i.e. a marble and a brick) are dropped from the same height at the same time, which would hit the ground first?

A) The heaviest object would hit the ground first because it weighs more.
B) Both objects will hit the ground at the same time, regardless of their mass.
C) The lightest object will hit the ground first because the larger mass cannot move through the air a quickly.
D) Whichever object hits the ground first is random and cannot be predicted.
E) None of the above are correct.

Question 11

Gravity affects what components of projectile motion?

A) Vertical only
B) Horizontal only
C) Vertical and horizontal
D) Gravity does not affect any components of projectile motion
E) Gravity increases an object's inertia

Question 12

Which of the following sports would be least likely to be affected significantly by a 'tail wind'

A) Javelin
B) Discus
C) Long jump
D) High jump
E) Hammer throw

Question 13

According to Newton's law of gravitation, a large mass such as the Earth exerts a gravitational pull on smaller masses (such as people and objects), but we don't exert any such gravitational force on the Earth.

Question 14

Any two objects exert a gravitational force of attraction on each other. The magnitude of this force is inversely proportional to the square of the masses of the two objects and proportional to the distance between them.

Question 15

The attractive force between Earth and a large boulder will be greater than the attractive force between the Earth and a golf ball. However, the acceleration during free-fall of the golf ball and the boulder will still remain the same if they were dropped from the same height.

Question 16

Calculate the weight of the person with a mass of 68kg standing on Earth's surface (acceleration due to gravity = 9.81m/s²), and on the moon (acceleration due to gravity 1.62m/s²)

Question 17

Most of the time in human movement, the effect of air resistance is considered negligible. Name two sporting examples where the effect of air resistance may be significant.

Question 18

Rearrange the following equation (found in the section 'uniformly accelerated and projectile motion') to calculate how long it would take for an object to reach the ground when dropped from a height of 3.5m.
D = V₁t + ½at²
where:
D = Distance from ground (3.5m)
V₁ = Initial velocity (0)
t = time in flight
a = acceleration (9.81m/s²)

Question 19

A training shoe is raised on a hinged surface (inclined plane), until it begins to slide. Immediately before the shoe begins to slide the angle of the surface to the horizontal is 47°. What is the coefficient of static friction (µs) between the shoe and the surface?

A) 0.123
B) 0.731
C) 0.682
D) 1.072
E) -0.124

Question 20

A basketball player exerts a downward force of 2550 N during a cutting movement in which the coefficient of static friction (µs) between their shoe and the court surface is 0.95. What is the maximal sideways force that the player can exert before their shoe slides on the surface?

A) 2422.6 N
B) 2684.21 N
C) 2422.5 N
D) 2550.95 N
E) 2549.05 N

Question 21

A bobsleigh (mass = 430 kg) is pushed across a horizontal (ice) surface with a horizontal force of 1927 N. If the coefficient of static friction (µs) and coefficient of dynamic (kinetic) friction (µk) between the bobsleigh and the ice are 0.071 and 0.068 respectively, what is the maximal friction force between the bobsleigh and the ice?

A) 286.8 N
B) 299.5 N
C) 30.5 N
D) 29.2 N
E) 2357 N

Question 22

A bobsleigh (mass = 430 kg) is pushed across a horizontal (ice) surface with a horizontal force of 1927 N. If the coefficient of static friction (µs) and coefficient of dynamic (kinetic) friction (µk) between the bobsleigh and the ice are 0.071 and 0.068 respectively, what is the friction force between the bobsleigh and the ice whilst being pushed?

A) 286.8 N
B) 299.5 N
C) 30.5 N
D) 29.2 N
E) 2357 N

Question 23

A bobsleigh (mass = 430 kg) is pushed across a horizontal (ice) surface with a horizontal force of 1927 N. If the coefficient of static friction (µs) and coefficient of dynamic (kinetic) friction (µk) between the bobsleigh and the ice are 0.071 and 0.068 respectively, what is the horizontal acceleration of bobsleigh?

A) 4.48 m/s²
B) 1640 m/s²
C) 2290 m/s²
D) 3.81 m/s²
E) 287 m/s²

Question 24

Impulse can be increased by which of the following?

A) An increase in force
B) A decrease in force
C) An increase in the time that force is applied
D) A decrease in time that force is applied
E) A and C are correct

Question 25

The linear momentum possessed by an object is a measure of what?

A) The horizontal acceleration of the object multiplied by the acceleration due to gravity
B) the object's mass multiplied by the object's linear velocity
C) The force applied by the object as a result of its linear velocity
D) The object's mass minus the object's linear velocity
E) The object's mass multiplied by the impulse applied

Question 26

Which of the following equations represents impulse (as equal to the change in momentum)

A) W = m x g
B) F = ma
C) p = m x v
D) Ft = mv₂ - mv₁
E) ∑F = 0

Question 27

A force of 20N applied over a period of 4 seconds would have the same impulse as:

A) A force of 30N applied over 2 seconds
B) A force of 10N applied over 10 seconds
C) A force of 40N applied over 2 seconds
D) A force of 60N applied over 1 second
E) A force of 90N applied over 1 second

Question 28

Two basketballs are thrown across the court. Basketball A is thrown at twice the velocity of basketball B. Both basketballs have the same mass. In this case basketball B has the greater momentum.

Question 29

An athlete performing a javelin throw may adjust their technique throughout the run-up and throw in order to increase the time of force application on the javelin. This should in turn increase the release velocity of the javelin (providing the average force is not significantly reduced).

Question 30

In sport and human movement it is always beneficial to create large amounts of impulse.

Question 31

Briefly describe the impulse-momentum relationship.

Question 32

A rugby player runs into a head-on tackle with another player that is running with the ball during a game. Player A (going for tackle) has a body mass of 98kg and runs at a velocity of 3.5 m/s. Player B (carrying the ball) has a body mass of 82kg and runs at a velocity of 4 m/s. Use the formula 'momentum = mass x velocity' (p = m × v) to calculate the linear momentum of each player as they run and comment on the implications of the results on the possible outcomes of the tackle.

Question 33

When performing a vertical jump on a force plate there are several interesting features of the force trace. At the beginning of the jump the force trace will become negative (i.e. it drops below the 1 × body weight line). Briefly describe what is happening during this part of the movement and why it is seen as a negative value on the force trace.

Question 34

A bobsleigh has a mass of 150 kg. The mass of its two crew members are 95 kg and 98 kg. What is the momentum of the bobsleigh and crew if it is travelling at 8 m/s.

A) 2744 kg·m/s
B) 343 kg·m/s
C) 1200 kg·m/s
D) 915 kg·m/s
E) 0 kg·m/s

Question 35

A cricket ball (mass = 0.16 kg) travels towards a catcher with a horizontal velocity of 30 m/s. What is its horizontal momentum immediately before it is caught?

A) 4.8 kg·m/s
B) 187.5 kg·m/s
C) 30.2 kg·m/s
D) 29.8 kg·m/s
E) 30.0 kg·m/s

Question 36

An athlete weighs 648 N and runs at a 15.48 km/hr. What is their momentum?

A) 10031 kg·m/s
B) 1022 kg·m/s
C) 2786 kg·m/s
D) 284 kg·m/s
E) 70.3 kg·m/s

Question 37

A rugby union player with a mass of 90 kg leaves the ground in preparation for a line out with a vertical velocity of 2.3 m/s. What is his vertical momentum at (i) the instant of take off, and (ii) the highest point of his jump.

A) 0 & 207 kg·m/s
B) 0 & 92.3 kg·m/s
C) 92.3 & 0 kg·m/s
D) 207 & 207 kg·m/s
E) 207 & 0 kg·m/s

Question 38

A cricketer (mass = 85 kg) leaps up to catch a ball (mass = 0.16 kg) travelling to the boundary at 27 m/s. Assuming the catch is successful what is the horizontal momentum of the player and ball immediately after the catch is taken, before the player lands on the ground?

A) 2299 kg·m/s
B) 85.16 kg·m/s
C) 4.32 kg·m/s
D) 0 kg·m/s
E) 0.006 kg·m/s

Question 39

A cricketer (mass = 85 kg) leaps up to catch a ball (mass = 0.16 kg) travelling to the boundary at 27 m/s. Assuming the catch is successful what is horizontal velocity of the player and ball immediately after the catch is taken, before the player lands on the ground?

A) 0.05 m/s
B) 4.32 m/s
C) 85.16 m/s
D) 0 m/s
E) 0.006 m/s

Question 40

Which of the following situations would be true according to Newton's law of acceleration?

A) A basketball is in flight (under the affect of gravity) and will continue to travel forward with constant horizontal velocity until stopped by another external force (such as hitting the ground, the hoop or being caught by another player)
B) A soccer player kicks a ball across the field. As the player applies a force to the ball with their foot, the ball applies an equal and opposite force onto the player's foot.
C) A javelin is in flight. Acceleration due to gravity affects the flight path of the javelin.
D) A volleyball player spikes the ball. The change of motion (momentum) of the ball is proportional to the amount of force applied by the player and inversely proportional to the mass of the ball.
E) A golf ball sits on the tee. As the ball applies a force to the tee it is balanced by an equal and opposite force applied by the tee to the ball (∑F = 0).

Question 41

Which of the following situations would be true according to Newton's law of inertia?

A) A basketball is in flight (under the affect of gravity) and will continue to travel forward with constant horizontal velocity until stopped by another external force (such as hitting the ground, the hoop or being caught by another player)
B) A soccer player kicks a ball across the field. As the player applies a force to the ball with their foot, the ball applies an equal and opposite force onto the player's foot.
C) A javelin is in flight. Acceleration due to gravity affects the horizontal component of the javelin's flight.
D) A volleyball player spikes the ball. The change of motion (momentum) of the ball is proportional to the amount of force applied by the player and inversely proportional to the mass of the ball.
E) A shot-putter uses specific technique to maximise the distance the shot put is thrown. One aspect of this technique involves increasing the amount of time that they apply the force on the shot put so as to increase the impulse.

Question 42

Which of the following situations would be true according to Newton's law of reaction?

A) A basketball is in flight (under the affect of gravity) and will continue to travel forward with constant horizontal velocity until stopped by another external force (such as hitting the ground, the hoop or being caught by another player)
B) A soccer player kicks a ball across the field. As the player applies a force to the ball with their foot, the ball applies an equal and opposite force onto the player's foot.
C) A javelin is in flight. Acceleration due to gravity can affect the vertical component of the javelin's flight but not the horizontal component.
D) A volleyball player spikes the ball. The change of motion (momentum) of the ball is proportional to the amount of force applied by the player and inversely proportional to the mass of the ball.
E) A shot-putter uses specific technique to maximise the distance the shot put is thrown. One aspect of this technique involves increasing the amount of time that they apply the force on the shot put so as to increase the impulse.

Question 43

When a force is applied to an object, such as the force applied to a golf ball from a golf club, it is being accelerated (i.e. from the unmoving to moving). Once the ball leaves the club and the force is no longer applied, the ball is no longer accelerating and moves at a constant horizontal velocity (in the absence of air resistance).

Question 44

Forces always act in single isolation.

Question 45

The force from gravity does not affect the horizontal motion of an object in flight.

Question 46

The formula derived from Newton's second law of motion is F = ma.

Question 47

A Rugby player (Player A) is running with the ball in his or her hands. Player B runs at Player A for a front-on tackle and tackles Player A to the ground. Considering the ball was not touched by Player B, if Player A lost his grip of the ball at the point of impact between the two players, which direction is the ball likely to travel in? Discuss this in respect to one or more of Newton's laws.

Question 48

A tennis player hits a tennis ball with a racket and the ball and racket are in contact with each other for 0.25 seconds. Use the formula ∑F = ma to calculate the force applied to the ball by the racket using the information below.
Mass of the tennis ball: 58 gm (0.058 kg)
Acceleration of tennis ball: 140m/s²

Question 49

A tennis player serves a ball at a speed of 224km/h. The ball reached the other player 20m across the court - how long did it take for the ball to reach the other player.