F = m·a (short quiz)

If the car is not moving, we can be sure that...

• ... there are no forces in horizontal direction

• ... there are no forces in any direction

• ... the man's force is equal to friction

• ... the man's force is equal to the car's weight

If the car starts moving (from 0 to 3 km/h), we can be sure that...

• ... there are no forces in horizontal direction

• ... the man's force is stronger than friction

• ... the man's force is equal to friction

• ... the man's force is equal to the car's weight

If the car is moving with constant speed (v=3 km/h), we can be sure that...

• ... there are no forces in horizontal direction

• ... the man's force is stronger than friction

• ... the man's force is equal to friction

• ... the man's force is equal to the car's weight

If two people get into the car and the man pushes with the same force as before...

• ... acceleration will be impossible

• ... it will accelerate THE SAME than with the empty car

• ... it will accelerate MORE than with the empty car

• ... it will accelerate LESS than with the empty car

Will the speed of the jumper increase?

• No, their velocity will be constant

• Yes: downwards

• Yes: upwards

• Yes: both downwards and to the right

Will the speed of the swimmer increase?

• No, their velocity will be constant

• Yes: downwards

• Yes: upwards

• Yes: to the left

Will the speed of the car increase?

• No, its velocity will be constant

• Yes: downwards and to the left

• Yes: upwards and to the right

• It is impossible to know just with this information