Page 124 - Big Ideas Year 10 sciPAD 2025

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124 SCIPAD - BIG IDEAS - BOOK 2
FORCES AND MOTION
Unbalanced Forces Cause Change
If forces acting on an object are the same size but are acting in opposite directions they are
described as balanced forces. When forces are balanced, they cancel each other out. This
means that there will be no net force on the object. If the object is moving, it will be moving at a
constant speed. If it is not moving, it will remain stationary.
When forces on an object are unbalanced there is a net force and the object will accelerate or
decelerate. The example shows that the car will be moving forward with a net force of 500 N.
1 000 N 1 000 N
1. Calculate the size and direction of the resultant force in the following examples.
(a)
(b)
(c)
(d)
2. Complete the following sentences by crossing out the incorrect words.
(a) If an object is moving at a constant speed and the forces are balanced, the object
will keep moving at a constant speed / accelerate / stop moving.
(b) In order for an object to accelerate, the forces must be balanced / unbalanced.
5 000 N
3 000 N
Size of force: 
Direction of force: 
Forces are balanced / unbalanced
Size of force: 
Direction of force: 
Forces are balanced / unbalanced
300 N
300 N
6 000 N 5 000 N
Size of force: 
Direction of force: 
Forces are balanced / unbalanced
2 000 N 8 000 N
Size of force: 
Direction of force: 
Forces are balanced / unbalanced
Because these forces are of equal size, but acting it
opposite directions, they cancel each out = Zero net force
500 N net force
500 N 1 000 N
Remember to show forces with
both a SIZE and DIRECTION
Because these forces are not equal size, some of the forward
force is cancelled out by the reverse force = 500 N net force
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