Forces & their Interactions (AQA GCSE Physics: Combined Science)

Explain the difference between mass and weight.

The weight of an object is directly proportional to its mass. 

Sketch a graph of this relationship on Figure 1.

Figure 1

Which value is represented by the gradient of the graph drawn in part (b)?

Tick (✓) one box.

The mass of the object
The weight of the object
The gravitational field strength
The centre of mass of the object

Figure 1 shows a football travelling through the air, to the right.

Figure 1

Two forces are acting on the ball: weight and air resistance.

Add two arrows to the diagram, showing the direction of the forces acting on the ball.

Make sure you label both forces.

Forces can be separated into two different categories: contact forces and non-contact forces.

Place one tick () in each row of the table below to show whether each force is a contact or a non-contact force.

State another example of a contact force and a non-contact force.

The football bounces off a wall, as shown in Figure 2.

Figure 2

The football exerts a force on the wall. 

The arrow in the diagram shows the size and direction of the force on the wall.

Add another arrow to the diagram showing the size and direction of the force exerted by the wall on the ball.

State the law that gives the relationship between the two forces acting on the ball and wall.

Figure 3 shows a wooden block with a mass of 250 grams

Figure 3

State the equation that links mass (m), weight (W) and gravitational field strength (g).

Calculate the weight of the block

Gravitational field strength = 9.8 N/kg

Give your answer to 2 significant figures.

Describe what is meant by the centre of mass of an object.

Add a cross (x) to Figure 3, showing the position of the centre of mass of the wooden block.

You may draw lines on the diagram showing how you found the centre of mass.

Some students carry out an experiment to test the stability of the wooden block.

The experiment involves placing the block on a wooden board, and then raising one end of the board until the block falls over, as shown in Figure 4.

Explain why the block is originally stable and then topples over when the angle is increased.

By taking careful measurements from either of the diagrams in Figure 3 or Figure 4, estimate the angle at which the block will topple over.

The students repeat the experiment, but this time they place the block on its side, as shown in Figure 5.

Figure 5

Explain how this will affect the stability of the wooden block.

Figure 7 shows a boy pulling a toy kite.

Figure 7

The kite has several forces acting on it, as shown in Figure 7

Figure 8 shows a vector diagram of one of these forces: the tension in the string.

Figure 8

Determine the magnitudes of the vertical and horizontal components of the tension.

Vertical component     =    _________ N

Horizontal component =   _________ N 

State the size of the drag force acting on the kite.

Drag force  =        _________  N

The kite has a mass of 150 g.

Calculate the weight of the kite.

Gravitational field strength = 9.8 N/kg

Give your answer to 2 significant figures.

Calculate the size of the lift force on the kite.

A moment later, the string on the kite breaks, releasing the kite.

At the moment of release, the tension in the string drops to zero, but the other forces all remain the same.

Determine the magnitude and direction of the force on the kite at the moment just after the string breaks.

Give the direction as an angle relative to the horizontal.

Resultant force = _________ N

Direction = _________ degrees (relative to the horizontal)

Another kite has two strings.

Two people take one string each, and pull the strings in different directions, as shown in Figure 9.

Figure 9

The forces exerted in each string are shown in Figure 10

By drawing a scale vector diagram, determine the resultant force of these two forces.

Show your working

Figure 1 shows a man attempting to push a large rock, and identifies some of the forces acting in this system.

Figure 1

Which forces in the list correctly identify the force pairs in this scenario?

Tick (✓) two boxes.

Force applied by man to rock & reaction force of rock.
Weight of rock & normal force of ground
Force of man's feet on ground & frictional force of ground
Weight of man & normal force of ground.

Higher Tier Only

David gets his friend Sam to help him move the rock. 

Figure 2 shows an aerial view of the position of the ropes used to pull the rock.

Figure 2

David and Sam pulled with equal force.

Draw an arrow on Figure 2 showing the direction of motion of the rock and explain why this is the case.

Higher Tier Only

A student throws a tennis ball vertically upwards and catches it as it returns to her.

Figure 1 shows the motion of the ball whilst it is in the air. 

Figure 1

Draw a free-body force diagram of the ball at position C.

Higher Tier Only

Explain the motion of the ball in terms of the forces acting upon it at each position throughout its journey.

Higher Tier Only

Figure 1 shows a skier being towed at a constant speed whilst sinking into the snow. 

Figure 1

State the name of each of the forces A - D acting on the skier.

Higher Tier Only

Which of the following statements are true about the forces acting on the skier?

Tick (✓) two boxes.

Force D > Force C
Force C > Force D
Force B > Force A
Force A = Force B