7. A 76- kg crate is at rest on the floor. It takes a minimum horizontal force o

Question

7. A 76- kg crate is at rest on the floor. It takes a minimum horizontal force of 350 N to make the crate slide. Calculate the coefficient of static friction between the crate and the floor.

8. A 1500 kg car is headed directly for a brick wall when the driver realizes the danger and slams on the brakes. The car's initial speed is 32 m/s, and the coefficient of kinetic friction between the tires and the road is 0.55. Determine how far the car travels while skidding to a stop. Assume it travels in a straight line.

Explanation / Answer

7.

mass of the crate m = 76 kg

the force is F = 350 N

let the coefficient of static friction be u_s

we know that

F = u_s x m x g

or u_s = (F/m x g)

where g = 9.8 m/s^2

8.

mass of the car m = 1500 kg

initial speed of car u = 32 m/s

the coefficient of kinetic friction is u_k = 0.55

let S be the distance travelled by car before coming to rest

we know that

v^2 - u^2 = 2 x u_k x g x S

or S = (v^2 - u^2/2 x u_k x g)

where v = 0 and g = 9.8 m/s^2

Related Questions

Navigate

• Browse (All)
• Browse 7
• Subjects

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