Page 122 - Big Ideas Year 10 sciPAD 2025

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122 SCIPAD - BIG IDEAS - BOOK 2
FORCES AND MOTION
Introduction to Forces
A force is a push, pull or twist applied to an object. They are measured in newtons (symbol: N).
Forces can be measured using a newton meter, and have both a size and a direction.
You cannot see a force but often you can see what it does. Forces can make things move, speed
up or make already moving objects slow down, change the direction they are moving in, and
even change the shape of things.
Forces can be categorised into two main groups:
•
Contact forces occur when the object transmitting the force is in contact with the object
receiving the force. Twisting a door handle involves contact forces.
•
Non-contact forces include gravity and magnetism - neither requires contact between objects
experiencing the force. Picking up paper clips with a magnet involves non-contact forces.
1. Define the term ‘force’. 

2. Name the unit in which forces are measured. 
3. Name the instrument used to measure the size of forces. 
4. Identify whether the force being described is a contact force or a non-contact force.
Description of Force Contact Non-contact
Screwdriver used to open a tin of paint.
Moon orbits around the Earth.
Electromagnet picks up metal at the recycling depot.
A foot pushes downwards on a bike pedal.
Comet pulled from deep in space towards the Sun.
Forces in Pairs
Forces usually act in pairs. Consider a sciPAD resting on a table as shown below.
5. Name the force that acts in the:
(a) Downwards direction. 
(b) Upwards direction. 
The book is exerting a force on the table in the downwards direction due to its
weight (the effect of gravity on its mass). This is called the weight force.
Because the book is not moving, the table must also be exerting an equal force
on the book in the upwards (opposite) direction. This is called the support force
(sometimes called the reaction force).
WEIGHT
SUPPORT
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