Question

An object has an initial velocity of 20 m/s how long is it accelerate at a constant rate of 4 m/s squared before the speed equals three times the initial speed

Answer 1

Given:

$v_i=20\:\rm m/s$

$v_f=60\:\rm m/s$

$a=4\:\rm m/s^2$

The time of accelerating

$$t=\frac{v_f-v_i}{a}=\frac{60\:\rm m/s-20\:\rm m/s}{4\:\rm m/s^2}=10\:\rm s$$