Forces
What is a force
A push or pull acting on an object.
What happens to an object when the forces acting on it are balanced?
Its motion does not change — it may remain still or continue moving at a constant speed.
What type of force pulls objects towards Earth?
Gravity.
What is the unit used to measure force?
Newtons (N).
What force keeps you standing on the ground?
Gravity
What are the two ways a force can act on an object?
Push or pull
Are these forces balanced or unbalanced? 5 N → ← 5 N
Balanced — equal forces in opposite directions.
What force slows objects down when two surfaces rub together?
Friction
Give one example of a force acting on an object.
Any suitable example, e.g. kicking a ball, gravity pulling an object down.
What is the difference between a physical and chemical change?
Physical changes do not create a new substance; chemical changes create new substances.
A soccer player kicks a stationary ball. What effect does the force have on the ball?
It causes the ball to move/change its motion.
A book is sitting still on a table. Are the forces on it balanced or unbalanced? Explain.
Balanced. Gravity pulls down and the table provides an upward support force.
Which force allows a magnet to attract a paperclip without touching it?
Magnetic force
What is the difference between contact and non-contact forces?
Contact forces require objects to touch; non-contact forces can act without touching.
What happens to particles when a solid is heated?
The particles gain energy and move faster/further apart.
A car is travelling forwards. A force of 800 N pushes forwards while friction provides 500 N backwards. What is the resultant force?
300N Up
A toy car has 10 N pushing forwards and 6 N pushing backwards. What is the resultant force and which direction will the car accelerate?
4 N forwards.
Name three different forces that could act on a falling object.
Gravity, air resistance, friction.
Explain why a moving bicycle eventually slows down when you stop pedalling.
Friction and air resistance act against its motion.
An astronaut weighs less on the Moon than Earth. Why?
The Moon has weaker gravity because it has much less mass than Earth.
Two people push a box in opposite directions. One pushes with 75 N and the other with 100 N. What is the resultant force? Which way will the box move?
25N Toward 75N person
An object has a resultant force of 0 N. Does this always mean the object is not moving? Explain.
No. An object can be moving at a constant speed in a straight line while the resultant force is 0 N.
Sort these into contact or non-contact forces: gravity, friction, magnetic, air resistance, push, electrostatic.
Why can a parachute slow a person down even though gravity is still pulling them towards Earth?
Air resistance increases as the parachute opens, creating a larger force opposing gravity.
A plant is placed in a dark cupboard for two weeks. Predict what will happen and explain why.
The plant will become unhealthy/possibly die because it cannot receive enough light for photosynthesis.