Question

If a car moving at 15 m/s skids to a stop after 20 m, how far will it skid if it is moving at 45 m/s? Assume that the braking force is constant. Group of answer choices 50 m 20 m 180 m 90 m 120 m

Answer 1

The car will skid at 80m

As we know that In mechanics, acceleration is the rate of change of the velocity of an object with respect to time.

It is a vector quantity

The velocity is the distance covered by an object per unit time

Given

Initial velocity (u) = 15m/s

Final Velocity (v) = 0m/s

Distance (s) = 20 m

Deceleration (a) =?

Now we know that ,

v² = u² + 2as

Substituting the value

0² = 15² + (2)*(a)*(20)

0 = 225 + 40a

Collecting the  like terms

0 – 235 = 40a

–225 = 40a

To find the value of a divide  both side 40

a = –225 / 50

a = –5.625 m/s²

Determination of the distance

Deceleration (a) = –5.625 m/s²

Initial velocity (u) = 30 m/s

Final velocity (v) = 0 m/s

Distance (s) =?

v² = u² + 2as

0² = 30² +(2 × –5.625 × s)

0 = 900 – 11.25s

Collecting  like terms

0 – 900 = –11.25s

–900 = –11.25s

To find the value of s divide both side by –11.25

s = –900 / –11.25

s = 80 m

Hence the car will skid 80 m

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