Deck 5: Special Topics

Question 1

If an athlete displaces a 20 kg kettle bell vertically by 70 cm, how much work has he done?

A) 123.5 Joules
B) 137.3 Joules
C) 113.8 Joules
D) 142.5 Joules
E) 130.2 Joules

Answer 1

B
Explanation: Using the equation:
Work = Force × displacement
W = (20 × 9.81) × 0.7
W = 137.3 Joules

Question 2

If a rugby player applies a force of 1050 N to a scrum sled and completes 2310 Joules of work, how far has he displaced the sled?

A) 1.8 metres
B) 2.5 metres
C) 2.0 metres
D) 2.2 metres
E) 2.8 metres

Answer 2

D
Explanation: Using the equation:
Work = Force × displacement
2310 = 1050 × d
2310/1050 = d
d = 2.2 metres

Question 3

If the rugby player applies the 2310 Joules over a 3.2 second time period, how much power has he produced?

A) 680.1 Watts
B) 815.2 Watts
C) 721.9 Watts
D) 782.2 Watts
E) 753.1 Watts

Answer 3

C
Explanation: Using the equation:
Power = Work / Time
Power = 2310 / 3.2
Power = 721.9 Watts

Question 4

In 2009, the 94 kg Jamaican sprinter, Usain Bolt, set the World Record for the 100 m sprint, posting a time of 9.58 s. Considering that he covered the first 10 m of this race in 1.89 s, how much linear kinetic energy did he use over this distance?

A) 1315.75 Joules
B) 1352.12 Joules
C) 1282.38 Joules
D) 1584.64 Joules
E) 1401.28 Joules

Question 5

A mountain biker performs a 110 m climb up a mountain trail and, in doing so, completes 82000 Joules of work. Given what is known about this performance, what is the cyclist's mass?

A) 85 kg
B) 76 kg
C) 80 kg
D) 72 kg
E) 81 kg

Question 6

If the mountain biker produced an average power of 285 Watts during the 110 m, how long, in minutes and seconds, did it take him to complete the climb?

A) 4 minutes, 25 seconds
B) 5 minutes, 1 second
C) 4 minutes, 48 seconds
D) 4 minutes, 3 seconds
E) 5 minutes, 23 seconds

Question 7

Bench pressing 60 kg in 0.5 seconds requires more power than bench pressing 80 kg in 0.8 seconds? Assume both masses are raised to a height of 75 cm.

Question 8

A 70 kg cyclist who rides up a 60 m long hill in 1 minutes 45 seconds produces a greater average power than an 85 kg cyclist who ascends the same hill in 2 minutes 3 seconds? Assume that the two cyclists are riding bicycles of equivalent mass.

Question 9

Provide a brief of the differences between positive and negative work.

Question 10

Briefly define the term 'power'.

Question 11

List the two types of potential energy and provide a brief description of each

Question 12

List the two types of kinetic energy and provide a brief description of each

Question 13

In 2009, the 94 kg Jamaican sprinter, Usain Bolt, set the 100 m sprint World Record with a time of 9.58 seconds. His linear velocities for the 50-70m and 90-100m splits were a) 12.3 m/s and b) 12.0 m/s, respectively. How many Joules of linear kinetic energy would he be using to complete each of these 10 m splits?

Question 14

Given the law of conservation of energy, the conversion of energy from one form to another leads to the total amount of energy

A) Increasing
B) Remaining the same
C) Decreasing
D) Initially increasing, before decreasing
E) Initially decreasing, before increasing

Question 15

An accomplished high-jumper is recorded as having a vertical take-off velocity of 6.12 m/s. In the absence of any significant external forces, how high would the athlete have jumped?

A) 1.63 m
B) 2.10 m
C) 1.85 m
D) 1.91 m
E) 1.74 m

Question 16

The conservation of mechanical energy typically applies to which sporting situation(s)?

A) Sprinting along an indoor running track
B) Performing aerial skills on a trampoline
C) Somersaulting from the high board into a swimming pool
D) Ice skating
E) All of these situations

Question 17

The amount of linear kinetic energy that a trampolist has at the instant they leave the surface of the trampoline net is greater than the gravitational potential energy at the highest point of the jump.

Question 18

During flight, an object's gravitational potential energy progressively increases.

Question 19

In the human body, the conversion of energy from chemical to mechanical energy is imperfect, meaning that the amount of chemical energy (e.g. adenosine triphosphate) is greater than the mechanical energy involved in producing a movement. Using the law of conservation of energy, briefly explain where the rest of the chemical energy goes.

Question 20

While performing a counter-movement vertical jump, an athlete records a jump height of 1.3 m. Calculate the athlete's vertical velocity at take-off.

Question 21

If an 80 kg person whose centre of mass was located 1.1 m above the ground was to maintain a rigid posture and fall forward at an angular velocity of 3.9 rad/s, calculate the moment of inertia.

Question 22

Calculate the linear velocity for a rigid object that is falling forward at an angular velocity of 3.5 rad/s. Assume that the centre of mass of the object is situated at a height of 0.70 m above the ground.

Question 23

Which of the following type of loading causes a material to shorten?

A) Compression
B) Tension
C) Bending
D) Shear
E) Torsion

Question 24

Which of the following type of loading causes a material to shorten on one side and lengthen on the other?

A) Compression
B) Tension
C) Bending
D) Shear
E) Torsion

Question 25

What is the stress experienced by a bone that has a tension load of 12kN applied to it over a cross-sectional area of 4 cm²?

A) 30,000 Pa
B) 300,000 Pa
C) 3,000,000 Pa
D) 30,000,000 Pa
E) 300,000,000 Pa

Question 26

What is the strain experienced if a 0.5 m bone is shortened to 0.498 m during compression loading?

A) 0.00004
B) 0.0004
C) 0.004
D) 0.04
E) 0.4

Question 27

What is 3,000,000 Pa expressed in Mega (M) Pa?

A) 0.3 MPa
B) 3 MPa
C) 30 MPa
D) 300 MPa
E) 3000 MPa

Question 28

Which of the Laws of Physics is the elastic region of a stress vs strain curve an example of?

A) Newton's 2nd Law
B) Hooke's Law
C) Boyle's Law
D) The First Law of Thermodynamics
E) Charles' Law

Question 29

What units would the Modulus of Elasticity be measured in?

A) Dimensionless
B) N
C) N/m
D) N·m²
E) N/m² or Pa

Question 30

A bone sample (depth = 8 mm, width = 12 mm, length = 15 mm) failed at 335 N during tensile loading. What are the cross sectional area (CSA) and the ultimate stress for the sample. Note: use the SI units, stated in the table.

A) 0.00096 m² & 3.49 MPa
B) 0.000096 m² & 3.49 MPa
C) 0.000096 m² & 34.9 MPa
D) 0.0096 m² & 3.49 MPa
E) 0.000096 m² & 349 Mpa

Question 31

Stress is measured in N·m^-2 and strain is dimensionless

Question 32

Stress is measured in N/m² and strain is represented as a proportion

Question 33

Stress is measured in Pa and strain is represented as a percentage

Question 34

If a collection of balls were dropped from the same height onto the same concrete surface, which of the following coefficient of restitution values would most likely correspond to the interaction resulting in the greatest rebound height?

A) e = 0.4
B) e = 0.6
C) e = 0.8
D) e = 0.2
E) e = 0.7

Question 35

The conservation of linear momentum principle states that

A) The momentum of an object will be unchanged following a collision
B) An object's momentum is unaffected by frictional forces
C) The combined momentum of colliding objects is unchanged after the event
D) The energy lost during a collision is the consequence of deformation
E) The combined momentum of colliding objects changes by an amount that is proportional to the sum of velocities after the event

Question 36

The coefficient of restitution will be lowest for:

A) A basketball dropped onto a concrete floor
B) A tennis ball dropped onto a sandy surface
C) A soccer ball dropped onto a sandy surface
D) A tennis ball dropped onto a concrete floor
E) A cricket ball dropped onto a concrete floor

Question 37

One would expect a bouncing tennis ball to have a higher rebound angle than incidence angle if the contact surface applied:

A) Higher frictional forces to the ball
B) Greater reaction forces to the ball
C) Lower frictional forces to the ball
D) Top spin to the ball
E) Lower lift forces to the ball

Question 38

Given the equation v'ball = vfoot * (mfoot/(mfoot + mball) * (1+e)), which of the following groupings for (i) mfoot/(mfoot + mball) and (ii) (1 + e) would result in the greatest initial velocity for the ball?

A) (i) 0.75 (ii) 1.50
B) (i) 0.82 (ii) 1.42
C) (i) 0.79 (ii) 1.60
D) (i) 0.88 (ii) 1.48
E) (i) 0.85 (ii) 1.50

Question 39

If an elite footballer could wear heavier boots without affecting his physical performance (e.g. running speed) or kicking mechanics, how might this affect the final velocity of the ball immediately following a maximal instep kick?

A) The ball's final velocity might go up or down
B) The ball's final velocity would be increased
C) The ball's final velocity would be unchanged
D) The ball's final velocity would be reduced
E) The mass of the footballer's boots would not influence the ball's final velocity

Question 40

A typical value for the term (1+e) when kicking a soccer ball is 1.5

Question 41

The coefficient of restitution is the first impact equation

Question 42

A head-on collision is an example of a central impact

Question 43

Briefly define the principle of 'conservation of linear momentum'.

Question 44

Briefly define what is meant by the term 'coefficient of restitution'.

Question 45

A 93 kg American football linebacker (mA) collides head-on with the 85 kg quarterback (mB) from the opposing team who is standing stationary at the time of impact. The collision causes the Quarterback to move at a velocity of 5.5 m/s in the same direction as his charging opponent, while the 93 kg athlete's velocity is slowed to 1.5 m/s. Disregarding the influence of other external forces; a) use the principle of conservation of momentum to determine the linebacker's initial velocity; and b) calculate the coefficient of restitution between the two footballers.

Question 46

During a game of billiards, a player propels the smooth white ball with a mass of 0.2 kg into the smooth wall surrounding the edge of the table. The ball collides with the wall at an angle of 35° and is travelling at a velocity of 3.5 m/s at the point of impact. If the coefficient of restitution is 0.65, determine the magnitude and direction of the ball's vertical velocity after its collision with the wall (i.e. v'y). Note: As both the ball and wall are smooth, assume that the horizontal component of the ball's velocity is unchanged after the collision (i.e. v'x); although it's direction will be opposite.

Question 47

The current maximum length of a tennis racket in professional competition is?

A) 80.35 cm
B) Any length
C) 73.66 cm
D) 58.26 cm
E) none of these

Question 48

The centre of percussion of a racket is broadly defined as?

A) The point on the racket that has the most vibration at impact with a ball
B) The point that is the 'sweet spot' in a racket
C) The point that, if contacted with the ball, makes the most effective shot
D) The point that is often in the handle of the racket
E) An imaginary point that is outside of the racket

Question 49

The dead zone of a tennis racket is?

A) An area that gives the most effective bounce when hitting a ball
B) An area that creates the most spin when hitting a ball
C) An area that when hitting a moving ball it is likely that the ball will stop suddenly
D) An area that is the most powerful area to hit a ball in tennis
E) An area that is in the handle of the racket and helps to reduce injury

Question 50

When would it be good to use the dead zone in hitting a ball in tennis?

A) At a volley shot
B) At a backhand shot
C) As a lob shot
D) At a smash shot
E) At the serve

Question 51

What is the "sweet spot' of a tennis racket?

A) A vibration node
B) A point of maximum spin
C) A point in the handle of the racket
D) A point outside of the racket
E) A point on the tennis court

Question 52

The moment of inertia of a tennis racket is given by the formula?

A) I = md/I C of G
B) I = I C of G + md²
C) I = I C of G x m x A²
D) I = I C of G + V-A
E) I = I C of M / I C of G

Question 53

In striking implements, the 'sweet spot' is the same point as the centre of percussion

Question 54

If a ball hits a racket at the centre of percussion, the vibrations transmitted to the hand/wrist/elbow will be zero

Question 55

The centre of percussion point on a bat or racket has important implications for performance

Question 56

The centre of percussion point on a bat or racket has important implications for injury prevention

Question 57

The maximum length of a tennis racket in current competition is 80 cm

Question 58

The centre of percussion in a racket or bat can change its position

Question 59

Determine the centre of percussion position on a tennis racket from the following data:
mass = 340 grams
position of the centre of mass from the grip position = 15.95 cm
moment of inertia about the x axis which is perpendicular to the sagittal plane (I c of g) = 0.0190 kg.m²

Question 60

Examine the internet for sports technology innovations that are designed to reduce the vibrations on the hand/wrist/elbow in a tennis racket

Question 61

Describe the term "sweet spot" that is commonly used in the sporting media/literature

Question 62

Describe a current issue within sport regarding the term centre of percussion and the 'sweet spot'