Motion, forces and energy

A student wishes to determine the density of a small solid object. First she finds the mass of the object. What should she do next?

• Attach the object to a spring and measure the change in length of the spring.

• Heat the object until it melts completely and measure how long it takes.

• Let the object fall through a distance of 1.0 m and measure how long it takes.

• Put the object in water in a measuring cylinder and measure the change in reading.

Answer explanation

Density measurement based on water displacement

A student has two light wooden rods with different diameters, a light metal block, a heavy metal block and a tray of damp sand. Each metal block is placed on each wooden rod in turn. The diagram shows the arrangement.

Which combination of block and rod causes the rod to sink the furthest into the sand?

• the heavy block on the rod with the larger diameter

• the heavy block on the rod with the smaller diameter

• the light block on the rod with the larger diameter

• the light block on the rod with the smaller diameter

Answer explanation

You are correct of you have thought in terms of pressure

Which source of energy is renewable?

• geothermal

• natural gas

• nuclear fission

• oil

A car is travelling along a straight, horizontal road at constant speed. Which statement about forces on the car is correct?

• There are no horizontal forces acting on the car.

• There is a resultant force on the car in the direction of its movement.

• There is a resultant force on the car in the direction opposite to its movement.

• There is no resultant force acting on the car.

Answer explanation

Newton's first and third laws of motion

A ball is thrown vertically upwards. The ball rises, stops, falls back down and hits soft ground without bouncing. Which energy transfers occur, starting just after the ball is released?

• kinetic to potential to kinetic to chemical

• kinetic to potential to kinetic to thermal

• potential to kinetic to potential to chemical

• potential to kinetic to potential to thermal

Answer explanation

Energy changes during motion

A gas is trapped in a container of constant volume. The temperature of the gas increases. What happens to the speed of the molecules, and what happens to the pressure of the gas?

• speed - decreases; pressure - decreases

• speed - decreases; pressure - increases

• speed - increases; pressure - decreases

• speed - increases; pressure - increases

Answer explanation

Kinetic Theory of Gases

Which option gives a unit for energy and a unit for power?

• energy - joule; power - newton

• energy - joule; power - watt

• energy - watt; power - joule

• energy - watt; power - ohm

The diagrams show all the forces acting on each of four objects. Which object is not in equilibrium?

• 
• 
• 
• 

Answer explanation

Consider net forces by vertical pairs and horizontal pairs

A man is standing in a bus that is moving forwards. The bus stops suddenly, causing the man to fall over. Which property of the man resists the change in his motion and in which direction does the man fall?

• property - mass; direction of fall - backwards

• property - mass; direction of fall - forwards

• property - weight; direction of fall - backwards

• property - weight; direction of fall - forwards

Answer explanation

Law of inertia

The diagram shows the speed-time graph for a car.

How far does the car travel in 30 seconds?

• 300 m

• 450 m

• 600 m

• 900 m

Answer explanation

Use Distance = Change in speed / time