1 What have I learned about forces?

Summary: Tags: science oxford-science student-book-7 physics Created: 2026-05-19 Last Updated: 2026-05-19

In this chapter, you have:

• learned that Forces act when objects interact and that forces come in pairs
• explained contact forces like Friction, drag forces, and tension using particles
• explained non-contact forces like Gravity and magnetic forces using fields
• discovered how Balanced and Unbalanced Forces explain how objects move – if forces are balanced, Speed or direction do not change; if forces are unbalanced, an object can speed up, slow down, or change direction.

Journey through forces What do I already know? - Pushes and pulls

• Friction
• Gravity This chapter - 1.1 Introduction to forces
• 1.2 Squashing and stretching
• 1.3 Drag forces and friction
• 1.4 Forces at a distance
• 1.5 Balanced and unbalanced What comes next? - Motion and Pressure
• Forces and motion
• Work and power
• Elastic Energy and Hooke’s

Figure 1

1. Sort the forces into contact forces and non-contact forces. magnetic forcefrictionair resistance gravityelectrostatic forceupthrust (2 marks)
2. Match the words to the definitions. mass force of Earth (gravity) acting on the mass of an object. Weight region where object experiences a force field amount of stuff (2 marks)
3. For each situation, decide whether the forces are balanced or unbalanced. a boat speeding up (1 mark)a boy floating in a swimming pool (1 mark)a cyclist going around a roundabout at a steady speed (1 mark)
4. A student is investigating friction. They put a block of wood on a ramp. They tilt the ramp until the block starts to move. They repeat the experiment using ramps with different types of surface. Name the independent variable and dependent variables. (2 marks)Name one control variable. (1 mark)Complete the conclusion for the experiment: The smoother the surface of the ramp, the blank the tilt before the block starts to move. (1 mark)Explain why the surface exerts a force on the block. (1 mark)Explain why the student should plot a bar chart to present their results. (1 mark)
5. Scientists are planning a mission to take astronauts to Mars. Suppose an astronaut has a mass of 65 kg on Earth. The Gravitational Field Strength on Earth is 10 N/kg. On Mars it is 3.8 N/kg. Calculate their weight on Earth. (2 marks)Describe and explain what will happen to their weight and mass when they go to Mars. (2 marks)
6. A student has a spring that is 3 cm long. When they exert a force of 2 N, the spring length changes to 4 cm. Calculate the extension. (1 mark)Calculate the extension when the force is doubled. (1 mark)
7. A student wants to make a newton meter. They coil a piece of wire around a pencil to make a spring. They put a 100 g mass on the spring. A 100 g mass has a weight of 1 N. They measure the extension. Describe how to measure the extension of a spring. (2 marks)Explain the difference between a mass of 100 g and a weight of 1 N. (2 marks) At the end of the experiment, the spring does not return to its original length when the masses are removed.Copy and complete the sentence. The spring has reached its blank blank (1 mark)
8. Another student decides to use an elastic band as a newton meter and plots the results. They hang masses on the elastic band and measure the extension. Figure 1 shows the graph of their results. Figure 1 Use the graph to explain why the elastic band cannot be used as a newton meter, but a spring can. (3 marks)Describe how the graph would change if the experiment were done in a place where the gravitational field strength were lower. Explain your answer. (2 marks)