Newton’s Equations of Motion

• s - displacement (m)

• u - initial velocity (m/s)

• v - final velocity (m/s)

• a - acceleration (m/s²)

• t - time (s)

v²-u²=2as

If starting at rest, u=0m/s (e.g. something dropped)

If stopping, v=0m/s (e.g. car coming to standstill)

If only force involved is gravity, a=9.8m/s²

Newton’s 1st Law: If no resultant force acts on an object, its motion will be constant (velocity will not change).

Terminal velocity: When this is true due to the drag force balancing the other force (e.g. weight).

Inertia: the tendency for an object’s motion to stay constant if no F.

Newton’s 2nd Law: F=ma

Force (N) = mass (kg) x acceleration (m/s²)

Practical:

1. Accelerate trolley in track with slotted mass on string over pulley.

2. Use light/photogates to measure acceleration.

3. Change force by removing masses and placing on trolley (to keep the total mass the same).

4. Plot F against a, gradient = total mass.

Newton’s 3rd Law: For every action (force), there is an equal and opposite reaction (force). This is NOT balanced forces.