Page 198 - Physics

Physics for Secondary Schools

4. The relationship between Revision exercise 8
displacement, average velocity 1. Choose the most correct answer in
and acceleration can be concisely items 1-3.
expressed mathematically in (i) The displacement of an object for a
equations. These can be manipulated round trip between two locations
to fi nd new useful relationships (a) is always greater than zero.
called the equations of motion of (b) is always less than zero.
a uniformly accelerating body. (c) is zero.
5. Equations of uniformly accelerated (d) can have any value.
motion are: (ii) A car is moving along a straight, level
road, with a constant acceleration.
v = u + at Which graph shows the motion of
1
s = ut + at 2 the car?
2 (a) (b)
v = 2 u + 2 2 as
distance speed
6. Motion under the effect of gravity
is uniformly accelerated motion.
All objects moving up or down 0 time 0 time
have the same acceleration due to (c) (d)
gravity. Hence, for a body moving
along gravity: distance speed
v = u + gt
1 0 0
h = ut + gt 2 time time
2 Figure 8.29

v = 2 u + 2 2gh (iii) A car begins to move. It speeds up
until it reaches a constant speed. It

and for a body moving against gravity, continues to travel at this constant
speed for the rest of the journey.
v = u - gt What happens to the acceleration

1 1 1 and what happens to the velocity of
hh ut – – gtgt 2 2 2
h = ut= ut=
gt
–
2 2 the car during the journey?
2
v 2 u= 2 – 2gh (a) Both the acceleration and the
velocity change.
For a free falling body, (b) Only the acceleration changes.
v = gt (c) Only the velocity changes.
(d) Neither the acceleration nor the
1 velocity changes.
h = gt 2
2 (iv) The following is the reason why
v = 2gh different objects in the air tend to
2
fall at the same time:

192
Student’s Book Form One

Physics Form 1 Final.indd 192 16/10/2024 20:58