The engine of a van of mass 400 kg cuts out when it is moving along a straight horizontal road with speed 16m s−1. The van comes to rest without the brakes being applied.
In a model of the situation it is assumed that the van is subject to a resistive force which has constant magnitude of 200 N.
a Find how long it takes the van to stop.
Here is my drawing of the system:
Now with all previous questions I've done there seemed to be some sort of force moving the van forward, however looking at the solutions for this question I see that they have only used the resistive force, I'm wondering why is there no force moving the van forward?
Similarly for this question part a)
A small stone of mass 400 g is projected vertically upwards from the bottom of a pond full of water with speed 10m s−1. As the stone moves through the water it experiences a constant resistance of magnitude 3 N. Assuming that the stone does not reach the surface of the pond, find
a) the greatest height above the bottom of the pond that the stone reaches,
Is there no force moving the particle up the water? Or is F just the forces that they have given us.
If anyone could clear this up thanks
Last edited by thorn0123; 02-07-2012 at 21:18.