# Can someone help with this speed time graph

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#1
A car moves along a straight horizontal road. The car starts from rest at a fixed point A on the road and moves with constant acceleration for 30 seconds, reaching a speed of 15 m s−1. This speed is then maintained. When the car has been moving for 15 seconds a motorbike starts from rest at A and moves along the same road in the same direction as the car. The motorbike accelerates at 1.5 m s−2 so that it catches up with the car when the car has been moving for T seconds.

(a) Using the same axes, sketch the speed-time graph of the car and the speed-time graph of the motorbike up to the time when the motorbike catches up with the car

For the motorcycle why is the graph reaching a point and then coming back to zero speed, they never said that the motorcycle comes to rest ? Why isn’t it just a straight line from 15s to Ts
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2 years ago
#2
the motorcycle graph should end at T s. The vertical line at T s would not be physically possible (instantaneous braking) and there is nothing in the question to say what happens, so just ignore it and it is a straight line from 15 to T.?

(Original post by studentzz123)
A car moves along a straight horizontal road. The car starts from rest at a fixed point A on the road and moves with constant acceleration for 30 seconds, reaching a speed of 15 m s−1. This speed is then maintained. When the car has been moving for 15 seconds a motorbike starts from rest at A and moves along the same road in the same direction as the car. The motorbike accelerates at 1.5 m s−2 so that it catches up with the car when the car has been moving for T seconds.

(a) Using the same axes, sketch the speed-time graph of the car and the speed-time graph of the motorbike up to the time when the motorbike catches up with the car

For the motorcycle why is the graph reaching a point and then coming back to zero speed, they never said that the motorcycle comes to rest ? Why isn’t it just a straight line from 15s to Ts
Last edited by mqb2766; 2 years ago
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#3
So do we always assume that the Second vehicle reaches zero speed eventually ?
(Original post by mqb2766)
the motorcycle graph should end at T s. The vertical line at T s would not be physically possible (instantaneous braking) and there is nothing in the question to say what happens, so just ignore it and it is a straight line from 15 to T.?
0
2 years ago
#4
Don't think you assume anything. Just draw it until T then leave it there.
(Original post by studentzz123)
So do we always assume that the Second vehicle reaches zero speed eventually ?
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4 months ago
#5
Where is this question from please ??
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4 weeks ago
#6
bit late, but I think the reason why the vertical line is there is to show that it ends at t=T, just like the vertical line where t=30
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