Question

If a car accelerates at a uniform 4.0 m/s2, how long will it take to reach a speed of 80 km/hr, starting from rest?.

Answer 1

Answer:

5.6s

Explanation:

Step1: Identify the given parameters

acceleration(a) = 4m/s²

initial velocity (u)= 0 (since the car started from rest)

final velocity (v) = 80km/hr

final velocity(v) in m/s = $80\frac{(km)}{(hr)} X\frac{(1000m)}{(1km)} X\frac{(1 hr)}{(3600s)}$

= $\frac{80,000(m)}{3,600(s)}$

=22.22m/s

Step2: calculate the time it takes the car to attain speed of 80km/hr = 22.22m/s

acceleration(a) = change in velocity per time

$acceleration = \frac{(final velocity)-(initial velocity)}{time}$

$a= \frac{v-u}{t}$

$t=\frac{v-u}{a}$

$t=\frac{22.22-0}{4} (s)$

a= 5.555 seconds

a≅5.6s