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physics (force) form 4
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Balanced and Unbalanced Forces
Prepared By: SYAZA IZZATY ISMAIL
What is a force? A force is a push or a pull (measured in
newtons,N). Forces are represented by arrows (always in
pairs) which point the way the force is acting - the bigger the arrow, the bigger the force (balanced forces have equally sized arrows)
Balanced forces - stationary /
steady speed
Balanced forces - stationary / steady speed
Force
Forces come in pairs Forces have a magnitude and a
direction
5N, north (up) Magnitude: 5NDirection: north (up)
Balanced and Unbalanced Forces
Forces occur in pairs and they can be either balanced or unbalanced
Balanced Forces
Balanced forces do not cause change in motion
They are equal in size and opposite in direction
Unbalanced Forces An unbalanced force always causes a change in
motion
When unbalanced forces act in opposite directions you can find the net forceNet force:
Magnitude The difference between the two forces
Direction Direction of the largest force
Unbalanced Forces
3 N, right – 6 N, left = 3N, left
Unbalanced Forces
4 N, left – 10 N, right = 6N, right
Unbalanced Forces
5 N, right + 10 N, right =15N, right
EXAMPLE 1 In which of the pictures will the object move
- what direction and with what force?
1)The first has a balanced force: 2N – 2N = 0 (there is no movement)
2)The second has a force of: 4N - 1N = 3N (move to the right)
EXAMPLE 2 A hammer hits a nail with a downward force
of 50N - what is the size and direction of the force of the nail on the hammer?
Complete the sentences below using the keywords: downwards; equal; opposite; and upwards: -a. The force on a ladder resting against a
wall is an to the force of the wall on the ladder
b. A book is a rest on a table. The force of the book on the table is and the force of the table on the book is
equal
opposite
downwards
upwards
50N upwards
LET’S DO IT! When standing on some bathroom
scales they read 500N. i) What is the size and direction of the
force of the student on the scales? ii) What is the size and direction of the
force of the scales on the student? A lorry tows a broken-down car -
when the force of the lorry on the tow rope is 200N, what is the force of the tow rope on the lorry?
500N upwards
500N downwards
200N
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