Question 12
A bus takes a time of
25 s to reach a constant speed while travelling in a straight line. A graph of speed
v against time t is
shown.
Which graph shows the variation with t of
the resultant force F on the bus?
Reference: Past Exam Paper – November 2015 Paper 12 Q10
Solution:
Answer: A.
Resultant force F = ma
The resultant force is
proportional to the acceleration.
From the velocity-time graph,
the acceleration can be obtained from the gradient.
Time
t = 0 to t = 5s:
constant gradient, so the acceleration is constant (and thus, the force is also
constant) [B, C and D are incorrect]
Time
t = 5s to t = 10s:
gradient is constant (same as before), then the line becomes steeper indicating
a greater value of gradient. So, the acceleration (and the force) increases
from one constant value to a greater constant value (as shown in A).
Time
t = 10s to t = 55s:
constant gradient, so the acceleration (and force) is constant (same as just before)
Time
t = 15s to t = 25s:
decreasing gradient, so the acceleration (and force) is decreasing
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