Question

Which of the following cannot be the speed-time graph?
A.

B.

C.

Answer 1

Hint: We are asked to find out among the three given graphs, which is not a speed-time graph. To answer this question, you need to recall the concepts of speed and time and the slope obtained from a speed-time graph. Use these concepts to check each option one by one and select the graph which cannot be a speed-time graph.

Complete answer:
Given, three speed vs time graph, we are asked to find which of the given graphs cannot not be a speed-time graph.The slope of speed vs time gives us acceleration. Also, at a particular value of time a body can have only one value of speed. We will use these concepts to answer the given question.Let us check each option one by one.

Option A : Here, we observe that the slope of the graph increases at first and then after a point starts decreasing which means the acceleration increases at first and after some time the acceleration starts decreases. Therefore, this graph can be a speed-time graph.
Option B: Here, we observe speed increases with time, that is, the slope of the graph is increasing or we can say acceleration is increasing. Therefore, this graph can be a speed time graph.
Option C : Here, we observe from the graph that for one particular value of time, there are multiple values of speed which is impossible as a body can have one value of speed at a time. Therefore, this graph cannot be a speed-time graph.

Hence, the answer is option C.

Note:Remember, the slope of a speed-time graph gives us the value of acceleration and the slope of distance-time graph gives us the value of speed. Also, if a body is moving with uniform speed that is it is constant with respect to time then acceleration of the body will be zero and if distance covered by a body is constant with respect to time, then speed of the body will be zero.