Question 20
Two balls X and Y are moving towards each other with
speeds of 5 m s-1 and
15 m s-1
respectively.
They make a perfectly elastic head-on collision and ball
Y moves to the right with a speed of 7 m s-1.
What is the speed and direction of ball X after the
collision?
A
3 m s-1 to the left
B
13 m s-1 to the left
C
3 m s-1 to the right
D 13
m s-1 to
the right
Reference: Past Exam Paper – March 2019 Paper 12 Q8
Solution:
Answer:
B.
For a perfectly elastic head-on
collision,
Relative velocity of
separation = Relative velocity of approach
Initially, the two balls
are moving towards each other.
Relative velocity of
approach = 5 + 15 = 20 m s-1
After the collision, ball
Y moves to the right at a speed of 7 m s-1.
The relative velocity of
separation should be equal to the relative velocity of approach (= 20 m s-1).
Ball Y is moving to the right at 7 m s-1. So, ball X should move in
such a way to increase the increase the relative velocity of separation.
Ball X should move in the
opposite direction (i.e. to the left).
v + 7 = 20
Velocity v = 20 – 7 = 13 m
s-1
No comments:
Post a Comment
If it's a past exam question, do not include links to the paper. Only the reference.
Comments will only be published after moderation