A car starts from rest and accelerates uniformly to reach a speed of 21 m/s in 7.0 s. What was the speed of the object after 2.0 seconds?

Answer 1

The car's acceleration is:

a = (change in velocity)/(change in time) = (21-0)/7 = 3 m/s²

Speed after t seconds is:

v = a·t + v₀

1. v = velocity at time t (seconds)
2. a = acceleration = 3 m/s²
3. t = time = 2 sec
4. v₀ = starting velocity = 0 m/s (at rest)

Plug in the numbers to compute the answer.