Question

a body move with velocity 30 m/s applies break and stop in 20 sec . Find deacceleration and displacement covered .

Answer 1

Answer: deacceleration=-1.5 m/s²

Displacement covered=300m

Explanation:

let u be the initial velocity and v will the final velocity.

as the body stops in 20 seconds so the final velocity must be zero.

v=0,t=20sec,u=30m/s

As we know, v²-u²=2as

So,0²-(30)²=2as

-900=2as

s=-900/2a

s=-450/a

Again, s=ut+1/2at²

-450/a=(30*20)+1/2a*20²

-450/a=600+200a

-450=600a+200a²

200a²+600a+450=0

Taking 50 common,

50(4a²+12a+9)=0

4a²+12a+9=0

4a²+6a+6a+9=0

2a(2a+3)+3(2a+3)=0

(2a+3)(2a+3)=0

Therefore,a=-3/2=-1.5m/s²

s=-450/a

Substituting the value of a in s we get,

s=-450/-1.5=300m

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