Page 9 - Pra U STPM 2021 Penggal 1 - Physics

Physics Term 1 STPM Chapter 2 Kinematics
3. The acceleration of free fall is determined P
by timing the fall of a ball bearing using
photocells. The ball is released from the point Light X
P, and passes the point X and Y at time t 1 and beam
t 2 after being released. Find an expression for h Photo-cells
the acceleration due to gravity in terms of h, t 1 Y
and t 2 . Light
2 beam
Q

Graphical Methods

The motion of a body can be analysed by studying the various graphs for the motion:
(a) Displacement-time graph
(b) Velocity-time graph

Displacement-time Graph 2010/P1/Q2, 2014/P1/Q2

1. Informations that can be deduced from the displacement-time graph:
(a) The instantaneous displacement.
The displacement s at any time t can be obtained off the graph.
(b) The velocity = Gradient of the graph.
(c) The manner that the velocity changes with time from the shape of the graph.

2. The displacement-time (s-t) graphs of a few types of motion are as shown in Figure 2.4.
(a) s (b) s

t t
0 0
Constant velocity Increasing velocity
Gradient = constant Gradient increasing
(c) (d) s
s

0 t
0 t T 2T
Decreasing velocity Motion of a body projected vertically upwards and
(deceleration) then falling back to the ground. When t = T, the body
Gradient decreasing is at the highest point. When t = 2T, the body is back
on the ground.
Figure 2.4 Displacement-time graphs

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