6.3 SPM Practice (Long Questions)


Question 7:



The diagram above shows the speed-time graph of a moving object for 15 seconds. Find
(a)    the speed of the object at t = 9s.
(b)   the distance travel by the object for the first 12 seconds.

Solution:

(a)
The speed of the object at t = 9s is 6 ms-1

(b)
Distance travel by the object for the first 12 seconds
= Area under the speed-time graph
= Area of triangle
= ½ × 12 × 8
= 48 m


Question 8:


The diagram above shows the speed-time graph of a moving object for 15 seconds.
(a) Find the time interval when the object moves with constant speed.
(b) Find the acceleration from t = 6 s to t = 12 s.
(c) State the time when the object is stationary.

Solution:

(a)
Time interval when the object moves with constant speed
= 12 – 6
= 6 s

(b)
Acceleration from t=6s to t=12s = Gradient of speed-time graph = 66 126 =0  ms 2 The moving object is moving  at a uniform speed

(c)

Time when the object is stationary is at 15 s.