Physics - Minimum distance?

Question

A rabbit is running on a straight line with velocity v=2m/s. A wolf is lying 40m from the line .The moment the rabbit is 40m far from the wolf , the wolf realizes it and starts to pursue it with v=2m/s .After 40 seconds, what is the minimum distance between them?

This is what I did:

displacement= Velocity x time--> 2 m/s x 40 s= 80 m

this is for the rabbit since it runs at a constant velocity throughout the run/chase

The wolf however starts from rest than accelerates to 2m/s and pursues rabbit therefore
displacement= avg. velocity x time= Vi+Vf/2 x time= 0+2m/s /2 x 40 s= 40 m

The minimum distance between the wolf and the rabbit after 40s is 80m-40m= 40m

The answer is not 40 meters and I don't know what else it can be. Please help!

Answer 1

You are making things unneccesarily difficult with your assumption about the wolf's acceleration. You are also assuming something in the process that isn't specified in the question, and which isn't a reasonable assumption to make, any way.

The question does not say "the wolf takes 40 seconds to accelerate to a speed of 2 m/s" (that's an awfully lame acceleration for a wolf), but rather that the wolf goes from rest to full speed instantaneously. Not exactly realistic, but far more so than 40 seconds. Realistically, the wolf would reach top speed in just a couple of seconds, so his acceleration can be ignored.

Now try your calculation again.

Answer 2

guessing that 'wolf is ... 40m from the line' means that the wolf is 40 OFF the line, then when wolfie runs to where the rabbit will BE in 40s...

you have two sides for a right triangle... 40M, 80M and... 89.4M? so the min distance for a stupid wolf who doesnt know algebra, is 9.4M