Question

A car moving with a velocity 20 m/s. The brakes are applied to retarded it at a rate of 20 m/s. What will be the velocity after the applying of the brake after 5 second.​

Answer 1

$\Large{\underline{\underline{\bf{Solution :}}}}$

★ Given :

Retardation (a) = -2 $\sf{ms^{-2}}$

Initial Velocity of car (u) = 20 $\sf{ms^{-1}}$

Time taken (t) = 5 seconds.

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★ To Find :

We have to find the speed of car after 5 seconds when break are applied.

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★ Solution :

Let change in velocity be x.

We know that,

$\small{\star{\boxed{\sf{Change \: in \: velocity = Retardation \times time}}}} \\ \\ \sf{x = -2 \times 5} \\ \\ \sf{x = -10 \: ms^{-1}}$

Here, -ve sign denotes the retardation.

$\rule{150}{2}$

Now,

If we subtract the initial velocity from final velocity of car we can get the speed of car.

$\sf{→ Speed = 20 - 10} \\ \\ \sf{→ Speed = 10 \: ms^{-1}}$

$\therefore$ Speed of car after retardation in 5 seconds is $\sf{10 \: ms^{-1}}$.

Answer 2

Answer:

The velocity of the car will be -80 m/s.

Explanation:

Referred to the attachment.