Y8 3.1 Forces and motion [Must Do]

What is needed for two forces to be balanced?

(Can choose more than one choice.)

• Two forces must be the same size.

• Two forces must be different sizes.

• Two forces must be in the same direction.

• Two forces must be in opposite directions.

A box sits on the ground. The box is not moving.

Match the following

• true

• There are no forces acting on the box.

• false

• There are balanced forces acting on the box.

• false

• There is an unbalanced force acting on the box.

Sofia is riding her bicycle. The driving force on the bicycle is balanced with the force of friction on the bicycle.

Label the names of the forces.

c

d

b

a

weight

contact force

friction and air resistance

driving force

Which of these can happen because of unbalanced forces?

​ (a)   , (b)   .

• A boat will slow down
• A football will change direction
• A car will move at a constant speed
• A book will not move on a desk

The diagram shows the forces on a car which is started to move forward.

The balanced forces are ​ (a)   and ​ (b)   .

The unbalanced forces are ​ (c)   and ​ (d)   .

• weight
• contact force
• driving force
• friction

Both team A and team B are pulling on the rope. The rope is not moving because forces are ​ (a)   ; force from team A is ​ (b)   and ​ (c)   to the force from team B.

• balanced
• equal
• opposite
• unbalanced
• larger
• smaller
• not opposite

The picture shows a to train moving around a circular track. The locomotive contains an electric motor that drives the train. The train moves in a circle at a constant speed.

Label the following forces on the train.

a

b

c

force that keep it moving in circle

friction

driving force

The helicopter begins to move upward when the upward force produced by its rotors is ​ (a)   than its weight.

• larger
• smaller