ScD Work, Energy and Power

The figure below shows a student running up a staircase at a CONSTANT SPEED. Which physical quantity increases while the student is running up the staircase?

• Inertia of the student

• Momentum of the student

• Kinetic energy of the student

• Gravitational potential energy of the student

1 J is equivalent to

• 1 kg m

• 1 kg s

• 1 N s

• 1 N m

Which of the following is true regarding the Principle of Conservation of Energy?

• Energy can be created or destroyed

• Total energy in a system stays the same

• Energy cannot be transformed from one kind to another

A moving car of mass 800 kg has energy of 250 k J. What is the velocity of the car?

• 2 ms^-1

• 10 ms^-1

• 25 ms^-1

• 20 ms^-1

• 30 ms^-1

Figure shows a pendulum oscillating between positions P and S. At which position does the bob possess both of kinetic energy and gravitational potential energy?

• P

• Q

• R

• S

The figure shows the path of a ball rolling down a smooth slope. The ball has the greatest change in gravitational potential energy between

• P and Q

• Q and R

• P and S

• R and T

Figure below shows a simple pendulum has a 150-g bob at the end of a string is released from a state of rest at point A. Determine the velocity of the bob at the lowest point B.

• $\sqrt{2}$ ms-1

• $\sqrt{3}$ ms-1

• 2 ms-1

• 3 ms-1

• 4 ms-1

A lift in a hotel can raise 8 people through a height of 20 m in 5 seconds. The lift plus passengers has a mass of 800 kg. What is the power of the lift motor?

• 40 W

• 8 000 W

• 40 000 W

• 32 000 W

• 160 000 W

A pump lifts 200 kg water per minute through a vertical height of 15 m. Calculate the power input rating of the pump if it is 65% efficient?

• 480 W

• 500 W

• 640 W

• 770 W

• 890 W

A moving lorry has kinetic energy. When the lorry stops, its kinetic energy is zero. This is because the kinetic energy

• is destroyed

• is used to stop the lorry.

• is converted to gravitational potential energy.

• is converted to heat energy as result of friction