Question

A body starts from rest and moves with an acceleration of 4ms-2 .

(a) In what time the body will acquire a speed of 80m/s?

(b) How much distance will it travel in this time?

Answer 1

initial velocity (u) :- 0m/s
acceleration (a) :- 4m/s -²

(a) final velocity (v) :- 80m/s 
time (t) :- ?
v = u + at (eq 1)
t = v-u/a
t = 80 - 0 /4
t = 80 / 4 
t = 20
ans) time taken is 20 seconds


(b) s = ut + 1/2 at²
 distance = (0)(20) + 1/2 (4)(20)(20)
distance = 0 + 800 
ans ) distance traveled in this time is 800 m.

Answer 2

v=80m/s   u=0    a=4m/s²

(a)   v=u+ at ---(1)
     substituting the values in (1) you get t=20s
(b)  s=ut+at²/2 ---(2)
     substituting the values in (2) you get s=800m

Hope this helped you...