1.2 Motion
Speed – Distance travelled per unit time
v=s/t
Average speed = total distance travelled / total time taken
Velocity – speed in a given direction
Speed = gradient from distance–time graph.
Distance travelled = area under a speed–time graph.
Acceleration = gradient of a speed–time graph.
The acceleration of free fall for an object near to the surface of the Earth is constant and is approximately 9.8m/s2.
Acceleration – Change in velocity per unit time.
Deceleration – Negative acceleration.
a=Δv/Δt
Without air resistance, objects fall at a constant speed (9.8m/s2).
With air resistance, objects accelerate until terminal velocity.
Terminal velocity - The speed of a falling object where there are no resultant forces acting. When terminal velocity is reached, air resistance and weight become equal, thus the velocity of the object is constant and acceleration is 0.