At 2: 00 pm a car's speedometer reads 30 mi/h. at 2: 20 pm it reads 50 mi/h. show that at some time between 2: 00 and 2: 20 the acceleration is exactly 60 mi/h2.let v(t) be the velocity of the car t hours after 2: 00 pm. then v(1/3) − v(0)/1/3 − 0 = . by the mean value theorem, there is a number c such that 0 < c < with v'(c) = . since v'(t) is the acceleration at time t, the acceleration c hours after 2: 00 pm is exactly 60 mi/h2.