Force Diagrams
Draw a force diagram of someone pushing a shopping trolley across a flat surface. Show gravity, applied force, and friction.
Downward arrow: Gravity; Forward arrow: Applied force; Backward arrow: Friction.
What is an unbalanced force? What effect does it have on an object’s motion?
An unbalanced force causes a change in motion—speed up, slow down or change direction.
Why does a soccer ball eventually stop after being kicked?
Friction with the ground and air resistance slow it down.
What role does friction play when riding a bike?
It slows the bike down and helps stop it when braking.
What happens to the motion of a bike when the rider stops pedalling?
It slows down due to friction and air resistance.
Sketch a diagram of a rock falling through a swimming pool. Label gravity and buoyant force with arrows.
Downward arrow: Gravity (large); Upward arrow: Buoyant force (smaller).
A bike is moving at a steady speed. Are the forces balanced or unbalanced? Explain.
Balanced—applied force and friction/air resistance are equal.
Why does a skateboard travel further on concrete than on grass?
Less friction on concrete means it can roll more easily.
What happens to air resistance when a skydiver opens their parachute?
It increases a lot, slowing the skydiver down.
A parachute opens mid-air. How do the forces change and what does this do to motion?
Air resistance increases, becomes stronger than gravity, and slows the person down.
Draw a diagram of a ball being pulled to the left with 45 N and to the right with 60 N. Label and calculate the net force.
Net force = 60 N – 45 N = 15 N to the right.
A bus is slowing down. Are the forces balanced or unbalanced? Why?
Unbalanced—friction and air resistance are stronger than the forward force
Why does a person bounce slightly when jumping on a trampoline?
The trampoline pushes back (reaction force) after you apply force down.
Explain how gravity and air resistance affect a ball as it flies through the air.
Gravity pulls it down; air resistance slows it in the opposite direction of motion.
A basketball hits the ground. How do the forces change before and after impact?
Before: gravity down. After: ground pushes up, causing bounce.
Draw a force diagram for a person skydiving after their parachute has opened. Label all relevant forces.
Large upward arrow: Air resistance; Smaller downward arrow: Gravity.
Two kids pull a rope—one with 40 N, the other with 70 N. What’s the net force? Who will win?
Net force = 30 N toward the stronger kid (70 N side). They will win.
What happens to the motion of a rollercoaster when it goes up a hill? Why?
It slows down due to gravity pulling it back and less forward force.
Why can you jump further on the Moon than on Earth? Use gravity and weight in your answer.
The Moon has less gravity, so you weigh less and can jump further.
Why does a book fall faster through air than through water? Think about resistance.
Water has more resistance (drag) than air, slowing it more.
A basketball is dropped from a balcony and hits the ground. Draw diagrams for before and after impact.
Before: Downward gravity only. After: Upward normal force from ground and downward gravity.
Describe a situation where multiple forces act on an object but it doesn't move. Explain why.
A book on a table: gravity pulls down, the table pushes up with equal force = balanced.
A person moves a heavy box using a trolley. How does the trolley help reduce the effort needed?
The wheels reduce friction, making it easier to push.
Why does a moving car stay at a constant speed when the engine keeps running and air resistance/friction are balanced?
The forward and backward forces are equal, so motion stays the same.
When you push a toy car and then let go, why does it eventually stop? Give two reasons.
Friction and air resistance slow it down until it stops.