Question

12. Four speed-time graphs are shown below in Fig. (a),
(b), (c) and (d).
Speed (m s-)
---Speed (ms-')
Time (s)
Time (s)
(a)
(b)
Speed (ms)
- Speed (ms)
Time (s)
- Time (s)
(d)
Which graph represents the following case?
(a) A ball thrown vertically upwards and returning
to the hand of the thrower
(b) An object decelerating to a constant speed and
then accelerating
(c) Uniform motion of a car
Justify your choice.​

Answer 1

Answer:

this is your answer

I have not the answer of c

sorry

Answer 2

Answer:

Option (a) - graph (a).

Option (b) - graph(d).

Option (c) - graph(b).

Explanation:

For option (a) :

The ball is experiencing only gravitational force. Therefore only acceleration is the acceleration due to gravity (g) which is constant 9.8 m/s^2. In the first half, when the ball is thrown upwards, it will have a positive speed that will decrease constantly as g acts opposite to the ball's motion.  Now in the second half, the ball reaches the topmost point and starts to fall downwards and g is acting along the motion of the ball, increasing the speed of the ball constantly. Therefore, the graph will first decrease then increase i.e. graph(a).

For option (b) :

The object is decelerating to a constant speed and then it is constant and then accelerating which is only depicted in graph (d).

For option (c) :

Uniform motion means the object is not experiencing any acceleration. No acceleration means the speed is constant with respect to time. The correct graph for this motion is the graph(b). In graph(b) the speed (y-coordinate)  is constant for different values of the time (X-coordinate).