Question

It takes 5 seconds to bring your car to a stop with an acceleration of -6 m/s^2. What was your intial velocity?

Answer 1

Answer: The initial velocity was 30 m/s

Step by step:

Starting from the general formula for velocity at time t with acceleration a and an initial velocity v_0, set up the equation with all knowns, then solve for v_0:

$v(t) = at+v_0\\v(5)=a\cdot5+v_0=-6\frac{m}{s^2}5s+v_0\\0\frac{m}{s}=-6\frac{m}{s^2}5s+v_0\\0\frac{m}{s}=-30\frac{m}{s}+v_0\\v_0=30\frac{m}{s}$