Page 21 - Pra U STPM 2021 Penggal 1 - Physics

Physics Term 1 STPM Chapter 2 Kinematics
7. A ball is thrown with a velocity of 8.0 m s at (b) Calculate the maximum range, R.
–1
60° to the horizontal. (c) What is its maximum height above the
(a) Draw on the same axes, a graph to ground when its range is maximum?
represent the variation with time of (Neglect air resistance)
(i) v H , the horizontal component of 9. An aeroplane is flying at a constant horizontal
velocity, –1
(ii) v V , the vertical component of velocity. velocity of 50 m s at a height of 1 000 m.
2 Identity your graphs and show suitable What is its horizontal distance from a target
values of velocity and time. on the ground, so that a parcel released from
(b) Use your graph to find the maximum the plane will hit the target.
height reached by the ball. 10. A coin is pushed off from the smooth
horizontal surface of a table of height 2.0 m.
8.
It falls and strikes the floor at a horizontal
distance of 3.2 m from the edge of the table.
v
Calculate
(a) the time taken by the coin to fall through
θ the air,
R (b) the speed at which the coin leaves the
table,
–1
A missile is fired with a speed of 500 m s from (c) the velocity of the coin when it strikes the
the ground. floor.
(a) What is the angle of projection θ for the
missile to achieve the maximum range?

Effects of Air Resistance
1. When a body moves through the air, the air resistance against the motion of the body is known as
the viscous drag.
2. The viscous drag on a body depends on
(a) shape of the body
Objects which are streamlined experience less drag.
(b) velocity of the body
The viscous drag is proportional to the square of the velocity.
3. When a body is released from rest and falls through the air, its velocity initially increases. As its
velocity increases, the viscous drag increases. The acceleration of the body decreases. Finally when the
acceleration is zero, the velocity is constant. This maximum constant velocity is known as terminal
velocity.
4. Figure 2.9 shows how the velocity of the body varies with time. Figure 2.10 shows the variation of
acceleration with time.
Velocity Acceleration
g

Terminal
velocity

0 Time 0 Time

Figure 2.9 Figure 2.10

50

02 STPM PHY T1.indd 50 4/9/18 8:19 AM