How Forces Affect Motion: common misconceptions

If your child says… “Just add all the force numbers.”

Ask together

Does a leftward pull help a rightward pull?

What’s true

Opposing forces subtract when finding the overall force.

If your child says… “Moving needs a bigger forward push.”

Ask together

Would a bigger forward force keep the speed unchanged?

What’s true

Steady straight motion needs no leftover forward force.

If your child says… “Friction never helps.”

Ask together

Would walking be easier if shoes slid freely?

What’s true

Friction can provide grip as well as slow sliding.

If your child says… “Inertia pushes passengers forwards.”

Ask together

Does continuing forwards need a new forward push?

What’s true

A passenger's body was moving before the bus stopped.

If your child says… “My force equals my speed.”

Ask together

Does multiplying mass by velocity give momentum or force?

What’s true

A net force changes momentum and does not measure speed.

If your child says… “Four kilograms means four newtons.”

Ask together

Does pushing harder change the trolley's mass?

What’s true

Kilograms measure mass, while newtons measure force.

If your child says… “A longer stop means a bigger force.”

Ask together

Which catch took longer, and which felt gentler?

What’s true

Compare catches with the same ball arriving at the same speed.

If your child says… “The paired forces cancel on each trolley.”

Ask together

Which trolley receives each force?

What’s true

Each force acts on a different object.