Forces & Energy

Which statement is correct?

• Mass is a force, measured in kilograms.

• Mass is a force, measured in newtons.

• Weight is a force, measured in kilograms.

• Weight is a force, measured in newtons.

Three children, X, Y and Z, are using a see-saw to compare their weights.

Which line in the table shows the correct order of the children’s weights?

heaviest ←→ lightest

• XY Z

• XZ Y

• YX Z

• YZ X

A spring is suspended from a stand. Loads are added and the extensions are measured.

Which graph shows the result of plotting extension against load?

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Which quantities are measured in the same unit?

• energy, power and work

• energy and power, but not work

• energy and work, but not power

• power and work, but not energy

Five identical bags of rice are balanced on a uniform beam by an object of mass 10kg. Two more identical bags of rice are added to the other five. The average position of the bags on the beam does not change. What mass now balances the bags?

• 3.5kg

• 7.0kg

• 12kg

• 14kg

Two farmers use an electrically powered elevator to lift bales of hay. All the bales of hay have the same mass

As sunset approaches, they increase the speed of the motor so that more bales are lifted up in a given time. How does this affect the work done in lifting each bale and the useful output power of the motor?

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Each diagram shows a metal plate with four parallel forces acting on it. These are the only forces acting on the plates. In which diagram is the plate in equilibrium?

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A student runs up a flight of stairs.

Which information is not needed to calculate the rate at which the student is doing work against gravity?

• the height of the flight of stairs

• the length of the flight of stairs

• the time taken to run up the stairs

• the weight of the student

The lamp in the diagram is not very stable and falls over easily.

• narrower base, higher centre of gravity

• narrower base, lower centre of gravity

• wider base, higher centre of gravity

• wider base, lower centre of gravity

A load is hung from a steel wire. The load is increased. The length of the wire increases until the limit of proportionality is reached. The load is now increased slightly. What happens?

• The extension of the wire increases and the wire no longer obeys Hooke’s law.

• The extension of the wire decreases and the wire no longer obeys Hooke’s law.

• The extension of the wire increases and it obeys Hooke’s law.

• The extension of the wire decreases and it obeys Hooke’s law.