Force-and-motion problem clinic
≈ 48 minForce-and-motion problem clinic
Newton's-law exam questions often hide a simple structure behind a story. First draw the selected object's free-body diagram. Second choose axes, usually along and perpendicular to motion. Third write one net-force equation per axis. State whether acceleration is zero or non-zero, and do not assume a normal force equals weight if another vertical force or acceleration exists. For a vehicle, trolley or lift, distinguish the force exerted by the engine or person from the net force after resistive forces. A final answer should include sign or direction, not only a magnitude.
Work it through
A 1200 kg car has a net forward force of 2400 N. Its acceleration is a = Fnet/m = 2400/1200 = 2.0 m s⁻² forward. If the driving force is 3000 N, total resistive force must be 600 N backward. The net force, not the driving force, is used in F = ma.
Mastery target
Translate a force story into a free-body diagram and signed net-force equation, then calculate acceleration or an unknown force with a physical check.
Which force belongs in F = ma for a car accelerating on a road?
Name the key physics term from Force-and-motion problem clinic that best fits the explanation and visual model.
A 1200 kg car has net force 2400 N forward. What is its acceleration in m s⁻²?
Which statement corrects a common misunderstanding in Force-and-motion problem clinic?