According to Newton's first law of motion, the net force acting on an object cannot be zero if its velocity is not constant (that is, if its speed or direction changes).

Have students work in pairs or small groups to assess whether or not the net force acting on each of the following objects is zero using evidence and Newton's first law.

Example: Is it non-zero or zero?

A container sitting atop a slope (Answer: zero)

With someone pushing on it horizontally, a large box remains at rest on the ground.

An automobile navigates a circular curve at a constant speed.

a the cart was moved steadily and quickly up a straight ramp

A young man riding a whirling Ferris wheel at a consistent speed is ____.

A raindrop falls at a consistent rate is _____.

Kicking two soccer balls of equal weight, but one harder than the other

Observing a 16-pound bowling ball being expelled onto the retrieval rack as opposed to an 8-lb bowling ball being ejected onto the retrieval rack

Running and pulling two wagons, one of which has one companion and the other has three.