An Object Moves along the X-Axis. Its X-Coordinate is given as a Fuction of time as x = 7t-3t2

Where x is in Metres and t is in Seconds. Its Average Speed over the Interval t=0 to t=4 is ?

(a) 5m/s

(b) -5m/s

© -169/24m/s

(d) 169/24m/s

x = 7t-3t^2 => v=dx/dt = 7-6t...so at t = 7/6 it turns back. Hence you can now get three positions: first the origin then extreme in positive x and then extreme in negative x at t=4. So you can get the distance travelled and hence the average speed.