# The speed of the skidding car when the brakes are applied. ### Precalculus: Mathematics for Calcu...

6th Edition
Stewart + 5 others
Publisher: Cengage Learning
ISBN: 9780840068071 ### Precalculus: Mathematics for Calcu...

6th Edition
Stewart + 5 others
Publisher: Cengage Learning
ISBN: 9780840068071

#### Solutions

Chapter 1.2, Problem 101E

(a)

To determine

## The speed of the skidding car when the brakes are applied.

Expert Solution

The speed of the skidding car when the brakes are applied is 28mi/h_.

### Explanation of Solution

Formula used:

The distance is calculated using the formula s=30fd.

Where s is the speed of the skidding car when the brakes were applied in mi/h, f is the coefficient of friction of the road, d is the distance that car skids after the brakes are suddenly applied in ft.

Calculation:

Given that, the distance that car skids on wet concrete road after the brakes are suddenly applied is 65ft.

Further, the coefficient of friction of wet concrete road is 0.4.

Substitute 0.4 for f, 65ft for d to calculate s as shown below.

s=30×0.4×65mi/h=780mi/h=27.928mi/h=28mi/h

Therefore, the speed of the skidding car when the brakes were applied is 28mi/h_.

(b)

To determine

### The distance that car skids on the wet tar road.

Expert Solution

The distance that car skids on the wet tar road is 167ft_.

### Explanation of Solution

Given that, the speed of the skidding car on wet tar road is 50mi/h.

Further note that, the coefficient of friction of wet concrete road is 0.5.

Substitute 0.5 for f, 50mi/h for s to calculate d in the formula mentioned in sub-part (a) as shown below.

d=(50)230×0.5ft=250015ft=166.67ft=167ft

Therefore, the distance that car skids on the wet tar road is 167ft_.

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