2. SPEED, VELOCITY & ACCELERATION

2. SPEED, VELOCITY & ACCELERATION
Key notes:
1. A scalar quantity has only a magnitude while a vector quantity has both a
magnitude and a direction.
2. Speed is distance moved per unit time. It is a scalar quantity.
3. Velocity is distance moved per unit time in a particular direction. It is a vector
quantity.
4. Displacement is the distance moved from a fixed point in a particular
direction.
5. In a displacement-time graph, gradient = velocity.
6. For a particle moving with a constant velocity away from the observer, the
gradient is a positive constant.
7. For a particle moving with a constant velocity towards the observer, the
gradient is a negative constant.
8. For a particle moving with an increasing velocity away from the observer, the
gradient is increasing.
9. For a particle moving with a decreasing velocity and eventually coming to a
stop, the gradient is decreasing and eventually becomes zero.
10. Acceleration, a = rate of change of velocity.
11. Without air resistance, all objects fall with the same acceleration when
released from rest.
12. The velocity-time graph of an object released from rest and falling freely will
show a constant increaseof velocity with time.
13. Due to air resistance, an object released from a height eventually reaches a
constant velocity called the terminal velocity.
Formulas:
 Speed = distance moved / time taken
v = d / t (m/s or km/h)
 Average speed = total distance moved / total time taken
 Velocity = distance moved in a particular direction / time taken
O LEVEL PHYSICS REVISION NOTES
 Acceleration = change of velocity / time taken for the change
= (final velocity - initial velocity) / time taken for the change
a = (v - u) / t or v = u + at
where a = final velocity
u = initial velocity
t = time taken
a = acceleration
 In a velocity-time graph, gradient = acceleration, and area under the graph =
distance travelled.
(1/2) x time (s) x velocity (m/s)