Question about motion along a straight line. If the displacement, s=t^2-4t. Find the minimum displacement.?
The minimum displacement should be 0 or -4? We should take the shortest distance between fixed point and particle or use ds/dt to find minimum displacement.
- Steve4PhysicsLv 72 months agoFavourite answer
Given that ‘s’ is the displacement, the minimum (smallest) value of displacement is -4 (which occurs when t=2).
If the question had been the minimum magnitude of displacement (minimum distance), the answer would be 0 (which occurs when t=0 or t=4s).
But I agree the question could be better-worded.
- KnrLv 42 months ago
since, given s = t’2 - 4 t, for the displacement to be minimum or maximum, the time derivative of displacement should be zero. Hence, ds/dt = 2 t - 4 = 0 , which gives t= 2 sec.
thus the displacement will be minimum when t = 2 sec and this gives s = 4 - 8 = - 4 m.