Energy, Work and Power

An object pulled along horizontal ground accelerates to the right.

The diagram shows the directions of the forces acting on the object.

Which force is multiplied by the distance moved to calculate the work done to increase the kinetic energy store?

Options

A   contact force
B   frictional force
C   pulling force
D   weight

A rock of mass $20\ \text{kg}$ is travelling in space at a speed of $6.0\ \text{m / s}$.

What is its kinetic energy?

Options

A   $60\ \text{J}$
B   $120\ \text{J}$
C   $360\ \text{J}$
D   $720\ \text{J}$

Which row shows an advantage and a disadvantage of using nuclear fuel to generate electrical power?

Options

Which row gives the definition of work done and the unit of work done?

Options

Seven energy sources are listed.

fossil fuel   hydroelectric   solar   nuclear   geothermal   wind   tides

How many of these energy sources are renewable energy sources?

Options

A   3
B   4
C   5
D   6

Energy is stored in batteries, fuel and food.

What is the name of this energy store?

Options

A   chemical
B   electrostatic
C   nuclear
D   thermal

A rocket has mass $M$ when empty. The rocket carries an additional mass $M$ of fuel.

The rocket and fuel travel at a speed $v$. When the engine of the rocket is fired, all of the fuel is expelled and the speed of the rocket increases to $2v$.

What happens to the kinetic energy of the rocket?

Options

A   It doubles.
B   It halves.
C   It increases by a factor of four.
D   It stays the same.

What is the definition of efficiency?

Options

A   $\text{efficiency} = \frac{\text{useful energy input}}{\text{total energy output}}$
B   $\text{efficiency} = \frac{\text{total energy input}}{\text{total energy output}}$
C   $\text{efficiency} = \frac{\text{useful energy output}}{\text{total energy input}}$
D   $\text{efficiency} = \frac{\text{total energy output}}{\text{total energy input}}$

An object of mass $m$ is lifted through a vertical distance $d$ in time $t$.

Which equation is used to calculate the power $P$ required to lift the object?

Options

A   $P = \frac{md}{gt}$
B   $P = \frac{mgd}{t}$
C   $P = \frac{dt}{mg}$
D   $P = \frac{m}{gdt}$

An object of mass $5.0\text{ kg}$ is pushed up a slope at a steady speed of $2.0\text{ m / s}$.

Which calculation gives the change in gravitational potential energy from the bottom to the top?

Options

A   $0.50 \times 5.0 \times 2.0$
B   $5.0 \times 9.8 \times 3.0$
C   $0.50 \times 5.0 \times 2.0^2$
D   $5.0 \times 9.8 \times 8.0$