6 Energy, work & power N2023 [End Unit Test]

A cyclist travels down a hill from rest at point X without pedaling. The cyclist applies his brakes and the cycle stops at point Y. Which energy transfers have taken place between X and Y?

• A. gravitational potential → kinetic → internal (thermal)

• B. gravitational potential → internal (thermal) → kinetic

• C. kinetic → gravitational potential → internal (thermal)

• D. kinetic → internal (thermal) → gravitational potential

A pump does 460,000 J of work to raise water to fill a tank. It takes 7 minutes to fill the tank. What is the power of the pump?

• 1.1 kW

• 66 kW

• 3200 kW

• 190,000 kW

What happens to the energy in the kinetic store and the gravitational potential store of the car as it moves from position X to position Y?

• energy in kinetic store decreases, energy in gravitational potential store decreases

• energy in kinetic store decreases, energy in gravitational potential store increases

• energy in kinetic store increases, energy in gravitational potential store decreases

• energy in kinetic store increases, energy in gravitational potential store increases

An electric car is charged overnight. In 8.0 hours, 180 MJ of energy is transferred. What is the power of the charger?

• 6.3 kW

• 380 kW

• 23 MW

• 1400 MW

An object of mass m falls from a higher shelf to a lower shelf. How much gravitational potential energy does the object lose?

• mgh₂

• (m/g)h₂

• (m/g)(h₁ - h₂)

• mg(h₁ - h₂)

A box is initially at rest at the top of a rough slope. The box slides down the slope. The weight of the box is 20 N. The slope is 4.0 m long and 2.0 m high. The box does 10 J of work against friction as it slides down the slope. What is the speed of the box as it reaches the bottom of the slope?

• 5.5 m/s

• 6.3 m/s

• 7.1 m/s

• 9.5 m/s

The mass of air hitting the blades of a wind turbine each second is 1.5 × 10⁴ kg. The speed of the air is 4.0 m/s. The density of air is 1.2 kg/m³. Which row gives the volume of the air hitting the blades each second and the kinetic energy of the air hitting the blades each second?

• Volume of air each second: 12500 m³ , Kinetic energy each second: 72000 J

• Volume of air each second: 12500 m³ , Kinetic energy each second: 120000 J

• Volume of air each second: 18000 m³, Kinetic energy each second: 72000 J

• Volume of air each second: 18000 m³, Kinetic energy each second: 120000 J

A boy uses a rope to pull an object of mass m up a slope. The rope is parallel to the slope. The tension in the rope is constant and of value F. The object moves a distance d along the slope and rises through a height h. How much work is done by the boy?

• F × d

• F × h

• m × g × h × d

• m × g × h^2

A microwave oven is rated at 900 watts. Which statement correctly describes the meaning of this value?

• 900 joules are transferred every second.

• 900 amperes are transferred every second.

• 900 volts are transferred every second.

• 900 ohms are transferred every second.

State the principle of conservation of energy.

• Energy can be created or destroyed.

• Energy can be transformed from one form to another, but the total energy remains constant.

• Energy is always increasing in a closed system.

• Energy is always decreasing in a closed system.