Page 4 - Pra U STPM 2021 Penggal 1 - Physics

Physics Term 1 STPM Chapter 2 Kinematics

2.1 Linear Motion

2010/P1/Q3, 2016/P1/Q2,Q18
Learning Outcomes

Students should be able to:
• derive and use equations of motion with constant acceleration
• sketch and use the graphs of displacement-time, velocity-time and acceleration-time for the motion of a body with constant
acceleration 2

1. Kinematics is the study of motion without considering the causes of the motion. Linear motion
is motion along a straight line.
2. The displacement s of a body from a point O to another point P is the distance moved by the body
along the straight line OP. Displacement s has both magnitude and direction, hence it is a vector.
3. The velocity v of a body is its rate of change of displacement. v

ds O ds P
Velocity, v = Figure 2.1
dt
Velocity v is also a vector, its direction is along the direction of the change in displacement ds. (Figure 2.1).
ds
4. The expression v = gives the instantaneous velocity. The instantaneous velocity of a car
dt
travelling along a straight road is shown by the speedometer.
5. If the time taken by a body to move through a displacement s is t, then
Final displacement, s
average velocity =
Time taken, t

Figure 2.2 The speedometer shows
the instantaneous
velocity

6. Acceleration a is the rate of change of velocity.
dv
Acceleration, a =
dt
Acceleration is also a vector. Its direction follows the direction of the change in velocity dv. When
the velocity of a body changes either in magnitude, or in direction, or both, the body accelerates.

Motion With Constant Acceleration

1. The acceleration of a body is uniform if the magnitude of the acceleration is constant and its direction
remains unchanged.

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