Question 1

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

Accepted Answer

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?

Accepted Answer

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?

Accepted Answer

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?

Accepted Answer

Calculate velocity over first 10m: v = 10 / 1.89 v = 5.291005 m/s Using the equation: Energylinear kinetic = 1/2 × m × v² Energylinear kinetic = 1/2 × 94 × 5.291005² Energylinear kinetic = 1315.75 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?

Accepted Answer

Using the equation:
Work = Force × displacement
82000 = (m × 9.81) × 110
82000 / 110 = m × 9.81 
745.4545 / 9.81 = m
m = 75.989 kg or 76 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?

Accepted Answer

Using the equation:
Power = Work / Time
285 = 82000 / t
285 × t = 82000
t = 82000 / 285
t = 287.719298 seconds
t = 4.7953 minutes
t = 4 minutes, 48 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.

Accepted Answer

Raising the 60 kg mass in 0.5 seconds would require a power of 882.9 Watts, while raising the 80 kg mass in 0.8 seconds would require 735.8 Watts.

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.

Accepted Answer

To ascend the hill in 1 minute 45 seconds, the 70 kg cyclist produces 392.4 Watts of power, while the 85 kg cyclist produces 406.8 Watts to climb the hill in 2 minutes 3 seconds.

Question 9

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

Accepted Answer

The answer of Provide a brief of the differences between...

Question 10

Briefly define the term 'power'.

Accepted Answer

The answer of Briefly define the term 'power'....

Question 11

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

Accepted Answer

The answer of List the two types of potential energy...

Question 12

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

Accepted Answer

The answer of List the two types of kinetic energy...

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?

Accepted Answer

The answer of In 2009, the 94 kg Jamaican sprinter,...

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

Accepted Answer

The law of conservation of energy states that energy can be neither created nor destroyed; that is, the total amount of energy remains constant.

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?

Accepted Answer

Using the equation:
vtake-off = √(2 × g × h)
6.12 = √(2 × 9.81 × h)
6.122 = 2 × 9.81 × h
37.45/(2 × 9.81) = h 
h = 1.91 m

Question 16

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

Accepted Answer

The conservation of mechanical energy does not apply to tasks where energy is lost to friction and cannot be used if the influence of air resistance is important (i.e. if relative air speeds exceed 5 m/s).

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.

Accepted Answer

The linear kinetic energy that the trampolinist has when they leave the bouncing surface of the trampoline (i.e. the net) is equal to the gravitational potential energy at the highest point of the jump (i.e. at the top of flight).

Question 18

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

Accepted Answer

During flight, the linear kinetic energy possessed by an object steadily decreases, while the gravitational kinetic energy progressively increases. The gradual change in these two quantities is such that the total mechanical energy remains constant (i.e. it is conserved).

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.

Accepted Answer

The answer of In the human body, the conversion of...

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.

Accepted Answer

The answer of While performing a counter-movement vertical jump, an...

Quiz 5: Special Topics