A car is speeding up and has an instantaneous velocity of 3.0m/s in the +x direction when a stopwatch reads 10.0s. It has a constant acceleration of 2.0m/s/s in the x+ direction. What is the speed when the stopwatch reads 13.0s?

Question

aaronq · Answer

the acceleration is 2 m/s^2, which means that every second the velocity increases by 2 m/s.

if the car is initially going at 3 m/s, after 1 second it's going at 5 m/s, then after another second it;s going at 7 m/s, etc.

anonymous · Answer

The car's initial velocity isn't 3m/s though, right? At 10 seconds, the velocity is 3m/s. So then going by your suggestion, the answer would be 9m/s at 13 seconds. I tried submitting this answer, but it's incorrect.

aaronq · Answer

sorry, the site is messed up. I'm not getting any notifications.

It should be correct though, under constant acceleration we can use the kinematic equation: $v_f=v_i+a\Delta t$

$v_f=3~m/s+(2~m/s^2)(3~s)=9~m/s$