Answer to Question #103152 in Mechanics | Relativity for Merl

Question

A small radio controlled car is moving to the right at 14 m/s at t=0s, with a constant acceleration of 2.0 m/s2 [L]. FIND:
The velocity of the car at t=6.0s
How long it takes the car to come to a rest.
At what time is the displacement of the car is equal to 40.0 m [R]

Answer 1

The velocity of the car at t=6.0s 

$$v(6)=v_0-at_0=14-2(6)=2\frac{m}{s}$$

Time is

$$T=\frac{v_0}{a}=\frac{14}{2}=7\ s$$

We have

$$s=v_0t-0.5at^2$$

$$40=14t-0.5(2)t^2$$

$$t_1=4\ s$$

$$t_2=10\ s$$

The second time will be when car returns backwards.