3.1 Forces and motion [Must do]

Hanna is cycling. Her legs provide a forward force of 150 N. Friction and air resistance give a combined force of 150 N. The resultant force is ​ (a)   and hence Hanna is moving at a ​ (b)   .​

• 0 N
• constant speed
• speed up
• slow down
• 300 N
• 150 N
• 300 N
• 150 N

Team A pull with a total force of 500 N and team B pull with a total force of 450 N. The resultant force is ​ (a)   . The rope starts to move towards Team ​ (b)   .

• 50 N
• A
• B
• 0 N
• 100 N

A car's engine provides a forward force on the car of 700 N. Friction and air resistance produce a combined backward force of 400 N. The resultant force is ​ (a)   . The car speed ​ (b)   .

• 300 N
• increases
• decreases
• remain the same
• 700 N
• 400 N

Calculate the resultant force on this box.

The resultant force is ​ (a)   .

The box is ​ (b)   .

• 5 N
• moving to the left
• not moving
• moving to the right
• 20 N
• 25 N

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

• false

• There is an unbalanced force acting on the box.

• true

• There are balanced forces acting on the box.

• false

• There are no forces 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

friction and air resistance

contact force

driving force

weight

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