IGCSE Physics module 1:Forces and Motion

Physics notes – Forces and Motion




Distance-Time Graphs
 Gradient = instantaneous speed (speed at any given moment)
- Negative gradient is returning back to the start point
 A horizontal line means stationary
 If the distance is 0 it is back at the starting point
 A curved line means it is accelerating
 To find instantaneous speed on a curved line, draw a tangent
and calculate the gradient

Speed = distance/time S = D/T
Velocity-Time Graphs
 Gradient = acceleration
- Negative
 Area between line and x-axis = displacement

,  Horizontal line = constant speed
 Curved line means acceleration is changing (jerk)

Acceleration = change in speed/time a = (v-u)/T


SUVAT Equations
1. V = u + at
2. S = 1/2(u+v)t
3. V2 = U2 +2as

How to solve: S = displacement
 Write SUVAT and fill in all the known values U = initial velocity
 Use the correct equation to find the unknown V = final velocity
 Watch out for + and – A = acceleration
T = time

Velocity and acceleration
 Speed is a scalar
 Speed = distance/time
 Velocity is a vector
 Velocity = displacement/time
 Acceleration is the rate of change of velocity
 Acceleration = change in speed/time



Average speed
When an object moves in a straight line at a steady speed, you can calculate its average speed
To calculate average speed over a journey do total distance/total time taken