1. 1
   A blacksmith uses a pair of iron tongs to hold a hot piece of metal firmly while hammering it against an anvil. A magnetic tool rack nearby holds some of the blacksmith's steel hammers in place without touching them directly.

   (a)

   A blacksmith uses a pair of tongs to hold a hot piece of metal firmly while hammering it on an anvil. The tongs grip the metal directly. What type of force is being exerted by the tongs on the metal?

   [1 mark]

   • AA contact force, because the tongs are physically touching the metal
   • BA non-contact force, because the metal is hot
   • CA non-contact force, because the tongs are made of metal
   • DA contact force, because the blacksmith is standing near the anvil

   (b)

   On the workshop wall, a magnetic tool rack holds several steel hammers in place, even though the rack does not touch the hammers directly; a small air gap remains between the magnets and the hammers. What type of force is holding the hammers to the rack?

   [1 mark]

   • AA non-contact force, because the magnetic force acts across the gap without the objects touching
   • BA contact force, because the hammers are made of steel
   • CA non-contact force, because gravity is pulling the hammers upward
   • DA contact force, because the rack is fixed to the wall

   (c)

   Explain the key difference between a contact force and a non-contact force, using the tongs gripping the metal and the magnetic rack holding the hammers as examples.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hiker walks up a steep, muddy hillside. Friction between their boots and the ground allows them to push off without slipping, while the gravitational force constantly pulls them back down the slope.

   (a)

   A hiker walks up a steep, muddy hillside. As they climb, the friction between their boots and the ground allows them to push off without slipping, while gravity constantly pulls them back down the slope. Which of these two forces acting on the hiker is a contact force?

   [1 mark]

   • AFriction between the boots and the ground
   • BThe gravitational force pulling the hiker downhill
   • CBoth friction and gravity are non-contact forces
   • DNeither force acts on the hiker while walking

   (b)

   The gravitational force pulling the hiker down the slope is described as acting on their centre of mass. Which of the following best describes gravitational force between the hiker and the Earth?

   [1 mark]

   • AA non-contact force, since it acts between the hiker and the Earth even though they are not touching at the centre of mass
   • BA contact force, since the hiker's boots are in contact with the ground
   • CA non-contact force that only acts when the hiker is moving
   • DA contact force that disappears if the hiker jumps into the air

   (c)

   State two other examples of non-contact forces, besides gravity, that the hiker might experience, and explain why each is classed as a non-contact force.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A crane on a construction site lifts a heavy steel girder using a cable, holding it stationary above the ground before lowering it into position.

   (a)

   Identify the forces acting on the girder while it hangs stationary from the cable, and state whether each is a contact or non-contact force.

   [3 marks]

   (b)

   The crane operator begins to lower the girder at a constant, steady speed. Describe how the forces acting on the girder change compared to when it was held stationary, and explain using the idea of balanced and unbalanced forces why the girder moves at a constant speed rather than accelerating.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A physics teacher sets up a classroom demonstration in which a small charged plastic rod is brought near a stream of falling water, and the water visibly bends towards the rod without anything touching it. The teacher then shows a second demonstration in which a bar magnet is brought close to a pile of iron filings on a table, and the filings jump up and cling to the magnet before it even touches the table.

   (a)

   Explain what is happening in this demonstration in terms of non-contact forces, and discuss how this demonstration illustrates the general difference between contact and non-contact forces studied in physics.

   [6 marks]

   (b)

   After the water demonstration, the teacher shows a second demonstration in which a bar magnet is brought close to a pile of iron filings on a table, and the filings jump up and cling to the magnet before it even touches the table. Compare this magnetic demonstration with the electrostatic water demonstration, discussing the similarities and differences between the two non-contact forces involved.

   [6 marks]

   Total for question 4: 12 marks

End of questions