Physics Help Please?????????????????????????

[匿名]

2015-12-10 12:11 am

These questions appeared on my physics hw as extra credit, any help solving them is appreciated. Thank you advanceeeeeeeeeeee:

Part A) A car is traveling at 64.4 mi/h on a horizontal highway. The acceleration of gravity is 9.8 m/s2 . If the coeﬃcient of friction between road and tires on a rainy day is 0.094, what is the minimum distance in which the car will stop? (1 mi = 1.609 km) Answer in units of m.

Part B) What is the stopping distance when the surface is dry and µdry = 0.566? Answer in units of m.

Thaaaanks

回答 (1)

NCS

2015-12-10 1:19 pm

✔ 最佳答案

64.4 mi/h = 28.8 m/s

A) acceleration a = µ*g
a = 0.094 * 9.8m/s² = 0.92 m/s²
so
s = v² / 2a = (28.8m/s)² / 2*0.92m/s² = 450 m

B) Now a = 0.566 * 9.8m/s² = 5.55 m/s²,
and s = (28.8m/s)² / 2*5.55m/s² = 74.8 m

Hope this helps!

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