Forces and Gravity
Forces are pushes or pulls that can change the motion, shape, or direction of objects, with gravity being the force that pulls all objects toward Earth.
What You Need to Know
Key Concept Diagram
A force is a push or pull that acts on an object and can change its speed, direction, or shape
Gravity is a non-contact force that pulls all objects with mass toward the centre of the Earth
The greater an object's mass, the greater the gravitational force acting on it (but all objects fall at the same rate in a vacuum)
Friction is a contact force that opposes motion between surfaces; it can slow objects down or prevent sliding
Key Vocabulary
Force
A push or pull that can change the motion or shape of an object
Gravity
The force of attraction between all objects with mass; on Earth it pulls objects downward
Mass
The amount of matter in an object, measured in kilograms (kg)
Friction
A force that resists the movement of one surface sliding over another
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
You drop a heavy rock and a light feather in a vacuum (no air). Which hits the ground first?
Question 2
Which of the following is a contact force?
Question 3
A ball is rolling along a flat surface and gradually slows down. Which force is causing this?
Key Concepts Summary
- ●A force is a push or pull that acts on an object and can change its speed, direction, or shape
- ●Gravity is a non-contact force that pulls all objects with mass toward the centre of the Earth
- ●The greater an object's mass, the greater the gravitational force acting on it (but all objects fall at the same rate in a vacuum)
- ●Friction is a contact force that opposes motion between surfaces; it can slow objects down or prevent sliding