A car starts from rest and travels for 5.2 s with a uniform acceleration of +1.6 m/s2. The driver then applies the brakes, causing a uniform acceleration of -2.1 m/s2. The breaks are applied for 1.50 s.

Question

A car starts from rest and travels for 5.2 s with a uniform acceleration of +1.6 m/s2. The driver then applies the brakes, causing a uniform acceleration of -2.1 m/s2. The breaks are applied for 1.50 s.
(a) How far has the car gone from its start?

R_scott · Accepted Answer

speed when brakes applied ... 5.2 s * 1.6 m/s^2 = 8.3 m/s

speed after braking ... 8.3 m/s + (1.50 s * -2.1 m/s^2) = 5.2 m/s

use the times and average speeds over the two segments
... to find the distance traveled

Jordan · Answer

Thank you, but I tried doing that and got an answer of 90.45 and said that was wrong... I'm not sure what I'm doing wrong.

R_scott · Answer

check your math the car is moving for a total of 6.7 s ... 90.45 is too high also, watch the sig figs ... probably a max of one decimal place in the answer