Singapore N(T)-Level Science, Forces and Motion: forces as pushes and pulls, speed, distance and time, pressure in solids, liquids and gases, and simple machines and levers

What this module is about

The Forces and Motion module of N(T)-Level Science (SEAB 5148) is about how things push, pull, move and press. As a Normal (Technical) module it keeps everything practical and everyday: why a box slows to a stop, how fast a cyclist is going, why a sharp knife cuts well, and how a crowbar lifts a heavy rock. The thread running through it is that forces and motion can be measured and calculated.

This overview ties the threads together and links to every dot point page in the module, each with its own worked answers and practice questions.

Forces as pushes and pulls

The module starts with forces, pushes and pulls. A force is a push or a pull, measured in newtons (N) with a spring balance (force meter). Common forces include friction (which opposes motion), weight (the pull of gravity) and air resistance. Forces can change an object's shape, speed or direction. Friction always acts in the opposite direction to the movement, which is why a sliding box slows down and stops.

Speed, distance and time

Next comes speed, distance and time. Speed is distance divided by time, measured in metres per second (m/s). You rearrange the formula to find whatever is missing: distance = speed times time, and time = distance divided by speed. You should also be able to read simple distance-time information, where a steeper line means a faster speed.

Pressure in solids, liquids and gases

The third dot point is pressure in solids, liquids and gases. Pressure is force divided by area, measured in pascals (Pa). The same force on a smaller area gives a higher pressure, which is why a sharp knife cuts easily and a drawing pin pushes into a wall. In liquids and gases, pressure acts in all directions and increases with depth, which is why a deep dam wall is built thicker at the bottom.

Simple machines and levers

The module finishes with simple machines and levers. A lever has a load, an effort and a pivot (fulcrum). When the effort is applied far from the pivot and the load is close to it, a small effort can move a large load, which is how a crowbar, a seesaw and a bottle opener work. Simple machines do not create energy; they let you use a smaller force over a longer distance.

How this module is examined

• Name the force and its direction. Friction and air resistance act opposite to motion; weight acts downwards.
• Use speed = distance / time cleanly. Show the formula, substitute, rearrange and quote m/s.
• Apply pressure = force / area. A smaller area gives a higher pressure; give the unit pascal.
• Identify load, effort and pivot. Explain how distance from the pivot makes lifting easier.

Check your knowledge

A mix of recall and application questions covering the module. Attempt them under timed conditions, then check against the solutions, and use the dot point pages for fuller practice.

1. Name the force that slows a sliding box and state its direction. (2 marks)
2. State the unit used to measure force. (1 mark)
3. A car travels 240 m in 20 s. Calculate its speed. (2 marks)
4. Write the formula for pressure and state its unit. (2 marks)
5. Explain why a sharp knife cuts more easily than a blunt one. (2 marks)
6. Name the three parts of a lever. (1 mark)