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Mechanics - Motion graphs

Hi everyone,

Is there anyone who can explain motion graphs to me please? I'm not sure how to do them, here is an example question:

'A man runs at a constant speed of 2ms^-1 for 10s, then accelerates at 2ms^-2 for 5s, then immediately decelerates at 3ms^-2 until he has stopped.'

I have to calculate the total distance - I've been advised to draw a graph but I've been given acceleration and velocity. Any advice?

Thank you! :smile:

Reply 1

davros

Original post by Little_Crazy_KK

Hasn't your teacher gone through any examples in class, or aren't there any in your textbook?

Basically, you want to be plotting velocity against time, which should be a set of straight lines of various slopes.

The slope of the graph at any point measures the acceleration; the area under the graph represents the distance travelled.

Reply 2

Atomic_H

OK with that you want to be plotting velocity in ms-1 and time in seconds. When he runs at a constant speed the line will be straight as he is running 2 ms/s right- he speed is not changing. Then when he accerates his speed is increasing so it will increase on the graph. 2m/s x the increase of 2ms for 5 seconds. When he decelerates you will need to work out his whole speed before that to work out how many seconds he needs to decelerate at 3ms for, then plot that time against that. (This should mean that as x- which is time increases on the graph- the y which is velocity decrease as he is slowing down. Hope this helps!

Atomic H