Review Quiz - Work, Energy & Power

Which of the following is true at the point where you reach the top of your jump on a trampoline?

• The mechanical energy is zero.

• The potential energy is at maximum.

• The kinetic energy and potential energy are equal.

• The potential energy is zero.

The conservation of mechanical energy must be considered when designing roller coasters. Looking at the diagram, which of the following statements is false?

• The gravitational potential energy is greatest at point A.

• The kinetic energy is greatest at points C and E.

• The gravitational potential energy is lowest at points C and E.

• The kinetic energy is greater than gravitational potential energy at point B.

Fathima throws a ball with a force of 63 N, a distance of 25 m. Maitha throws the ball with the same amount of force, but the ball only goes 17 m. Which girl does less work?

• They do the same amount of work.

• Fathima

• Maitha

• Neither girl does any work.

A 100 N force is applied at an angle of 30ᵒ to the horizontal to move a 15 kg block at a constant velocity. Determine the amount of work done in moving the block a horizontal distance of 5m.

• 250 J

• 433 J

• 500 J

• 636 J

Power is defined as the change in energy divided by the time required for the change, P = ΔE/T. Which of the following formulae cannot be used to solve for power?

• P = F X V

• P = W/t

• P = F x d/t

• P = F x V/t

A truck applies a force of 2000 N to pull a car out of a hole. The car is pulled 8 meters in 10 seconds. What power does the truck produce in order to move the car?

• 1600 W

• 1600 J

• 16000 W

• 16000 J

A ball of mass 0.5 kg falls from a height of 45 m. Using energy considerations, find the final velocity. Let g = 9.8 m/s².

• 44.1 m/s

• 29.7 m/s

• 21.0 m/s

• 2.97 m/s

A mechanical device requires 420 J of work to do 230 J of work in lifting a crate. What is the efficiency of the device?

• 55%

• 183%

• 0.55%

• 1.83%

What is the IMA (Ideal Mechanical Advantage) of the ramp shown in the diagram above?

• 0.22

• 4.5

• 14.0

• 22.0

A pulley system consisting of two fixed pulleys and two movable pulleys is used to lift a piano that has a 3200 N weight at a constant speed. If the effort force used to lift the piano is 800 N, what is the mechanical advantage of the system?

• ¼

• ½

• 4

• 8