[填空题]
The graph shows how the speed v of a car varies with time t.
1.State the difference between average and instantaneous accelerations.
2.Calculate the instantaneous acceleration of the car at t=1.0 s. The gradient of the tangent line = $m\,s^{-1}$
3.Determine, with explanation, whether the car covers more distance before or after the car reaches a constant speed.
