Identifying Forces (neglect small frictional forces and air resistance forces for now)

A box rests on a table. How many forces act on the box?
A. 0    B. 1    C. 2    D. 3    E. 4




A steel ball rolls across a horizontal marble table at constant speed. How many forces act on the ball?
A. 0    B. 1    C. 2    D. 3    E. 4



A skiier coasts downhill, gaining speed. How many forces act on the skiier?
A. 0    B. 1    C. 2    D. 3    E. 4

A skiier leaves the end of the ski jump and is at the highest point in mid air. How many forces act on the skiier?
A. 0    B. 1    C. 2    D. 3    E. 4

A skiier leaves the end of the ski jump and is on her way upward in mid air. How many forces act on the skiier?
A. 0    B. 1    C. 2    D. 3    E. 4





At an ice staking rink you give a (big) push to a broken-down Zamboni and it starts to slide across the ice. After it has left your (powerful) grasp, how many forces act on it as it it sliding across the ice?
A. 0    B. 1    C. 2    D. 3    E. 4

Newton's 1st law: A body acted upon by no net forces moves with constant velocity (which may be zero) and zero acceleration.

If the net force acting on a body (along the x, y, and z axes separately) is zero, it is said to be in equilibrium.

Intertia is the property of mass (matter) which resists changes in motion. Objects in motion remain in motion, objects at rest remain at rest unless acted upon by a net force.