The coefficient of static friction between a block of wood of mass 29.5-kg and a

Question

The coefficient of static friction between a block of wood of mass 29.5-kg and a rough table is 0.88. The table is slowly tilted until the block of wood starts to slide down the surface. At what angle o f the table with respect to the horizontal does the wood start to slide? Your answer should be given to the nearest tenth of a degree. To avoid hitting a pedestrian, a car driver slams on her brakes and comes to a complete stop after skidding 14 m. If the coefficient of kinetic friction between the car's tires and the road is 0.53, what was the speed of the car when the brakes were applied. (The car is old and does not have anti-lock brakes!) Give your answer to the nearest tenth of a m/s.

Explanation / Answer

First question: sum forces perpt to slope

N - m g cos theta = 0

N = m g cos theta

sum forces perp to slope

friction - m g sin theta = 0

if just about to slide friction = u N

u m g cos theta - m g sin theta = 0

sin theta = u cos theta

tan theta = u

theta = arctan(u) = arctan(0.88)=41.4 degrees

Second question.

friction = ma

u m g = ma

a = u g

v^2 = v0^2 + 2 a d

0 = v^2 + 2*-0.53*9.82*14

v=12.1

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.