AQA GCSE Physics: Forces

A skydiver jumps from a high aircraft and falls towards the ground. At first she accelerates, but after some time she reaches a constant speed called terminal velocity. She then opens her parachute, slows down, and finally falls at a new, lower constant speed.

Describe and explain, in terms of the forces acting on the skydiver, how her motion changes from the moment she jumps until she lands. Refer to weight, air resistance and resultant force in your answer. (6 marks)

A child sits on one side of a uniform see-saw, a perpendicular distance of 2.0 m from the central pivot. The child's weight is 400 N. (This question uses moments — Higher-tier content.)

(a) Calculate the moment of the child's weight about the pivot. Use $M = Fd$M=Fd. Show your working and give the unit. (2 marks)

(b) A second child of weight 500 N sits on the other side to balance the see-saw. Using the principle of moments, calculate how far from the pivot the second child must sit. (2 marks)

A car of mass 1200 kg has a resultant forward force of 3600 N acting on it.

(a) Calculate the acceleration of the car. Use $F = ma$F=ma. Show your working and give the unit. (2 marks)

(b) State what would happen to the acceleration (for the same resultant force) if the car carried extra passengers, increasing its mass. (1 mark)

A trolley of mass 0.80 kg is moving at 6.0 m/s. It collides with a wall and rebounds in the opposite direction at 4.0 m/s. The collision lasts 0.20 s. (This question uses momentum — Higher-tier content.)

Taking the initial direction of motion as positive, calculate the average resultant force exerted on the trolley by the wall during the collision. Use $p = mv$p=mv and $F = \dfrac{\Delta p}{\Delta t}$F=ΔtΔp​. Show your working and give the unit. (3 marks)

A crowbar is used as a lever to lift a heavy paving slab. The user pushes down on the long end of the bar, a long distance from the pivot, and the short end lifts the slab. (This question uses moments — Higher-tier content.)

Explain how a lever like this acts as a force multiplier, allowing a small effort to lift a large load. Refer to moments in your answer. (2 marks)

Physical quantities can be classified as scalars or vectors.

State the key difference between a scalar quantity and a vector quantity. (1 mark)