Along with the question I had asked a doubt. This is the doubt. How is it possible to construct a velocity-time graph when only the time is given? How did you assume that the initial velocity is 30m/s?

Asked by Suneel | 27th Jun, 2017, 12:24: PM

Expert Answer:

Your question was:
A ball is thrown up vertically and returns back to the thrower in 6 sec. assuming that there is no air friction plot velocity time graph.
From the graph calculate (i) deceleration (ii) acceleration (iii) Total distance covered by stone (iv) Average velocity.
The following are the steps to the solution:
-The total time of balls vertically upward and then downward motion of 6 secs is equally divided into 2 time frames for upward and downward motion respectively.
-The initial velocity of upward throw is 'u', final velocity is 'v'=0 as the ball just stops before setting up for the downward direction and time for upward motion when velocity becomes zero is 3 secs.
-By using v=u+at where a=g(for upward)= -9.8~ 10m/s2 and substiuting above values we get 'u'=30 m/s.
-When the upward motion just starts, velocity is 30 m/s, similarly find velocity at 1st and 2nd second.
-The corresponding velocities for the downward motion of the ball will be same as that of the upward.
-This is how we plot v-t graph, by calculating velocities at every second.

Answered by Abhijeet Mishra | 27th Jun, 2017, 06:22: PM

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