Question

A car travels first 10 seconds with uniform
acceleration of 2 m/s from rest on straight road
and then travels with zero acceleration for next
10 seconds. The average speed of entire journey
is
9
10​

Answer 1

Answer:

15 m/s

Explanation:

firstly there are two cases

(1) when it's accelerating

(2) when it's in constant speed

so we have to find distance of both of then then sum is divided into sum of time

as we know

a=(v-u)/t. here a= 2, u=0,t=10s

2=(v-0)/10

2×10=v

v= 20 m/s

as we also know

2as = v^2 - u^2.

2(2)(s) = (20)^2

4s = 400

s = 100

now second case constant speed

so distance travelled

s=d/t. as we find s = 20m/s

20= d/10

200m= d

now average speed

average speed= total distance/ total time

s= (100+200)/(10+10)

s= 300/20

s= 15m/s