A car starts from rest and accelerated uniformily to reach a speed of 21 m/s in 2.0 s. What was the speed of the object after 2.0 seconds

Answer 1

The speed after 2.0 seconds was given as 21 m/s in the problem statement! Perhaps you meant to ask, " What is the speed 2.0 seconds after reaching a speed of 21 m/s"?

Answer 2

x(t) = x₀ + v₀*t + 1/2*a₀*t^2

Above is the most widely applicable formula you will learn in intro physics. Learn it, use it, love it!

We can start by setting x(0) equal to 0m (this is a convenient orientation of our coordinate system):

x(0) = x₀ = 0m

Next the problem says the car starts at rest:

v₀ = 0m/s

At this point we are left with:

x(t) = 1/2*a₀*t^2

All that is left for you is to plug in the given values. Best of luck!