A puck slides on a surface for 5.6 m before it stops. If it was moving at a velo

Question

1. A puck slides on a surface for 5.6 m before it stops. If it was moving at a velocity of 15 m/s and has a mass of 1.2 kg, what is the force of friction exerted on the puck? There is a non-conservative work done on the puck equal to the change in kinetic energy, or:
2. If a tire on a semi-truck is 1.1 m. How many FULL rotations will the tire roll if the truck moves 24.5 meters?
3. A large circus ride has a centripetal acceleration at 6.0 m/s2. If the circular ride has a radius of 11.0 m, what is its velocity at the edge?
4. If a 56 diameter circular disk is uniformly angularly accelerating at a rate of 5.0 rad/s2, what will the final angular velocity be after 4.0 seconds if it starts at a rate of 10.0 rad/s? What angle is subtended over that time?
5. A 40.0 N force is applied to a 46.0 cm long torque wrench. What is the net torque applied to the nut? Also if this force is applied for 3.0 seconds and the bolt starts from rest and ends with an angular velocity of 0.5 rad/s, what is the bolt%u2019s moment of inertia?

Explanation / Answer

1) W = F*s*cos(180)

workdone = change in kinetic energy

0.5*m*v^2 = -F*s

F = -0.2*1.2*15^2/5.6 = -9.64 N.

negatice sign represents force is oppsite to the motion.

here work is dont by friction which is non-conservative.

2)here i am assuming d = 1.1 m

r = d/2 = 0.55m

let n is the no of full raotations

n*2*pi*r = 24.5

n = 24.5/(2*3.14*0.55) = 6.95 rotations

n = 6 full rotations.

3)a_rad = v^2/r

v = sqrt(a_rad*r) = 8.124 m/s

4) w2 = w1 + alfa*t

w2 = 10 + 5*4 = 30 rad/s

angular displacement, theta = w2^2 - w1^2/(2*alfa) = 80 rad


5)Torque, T = r*F*sin(90) = 0.46*40 = 18.4 N.m

alfa = (w2-w1)/t = 0.5/3 = 0.167 rad/s^2

T = I*alfa
I = T/alfa = 110.4 kg.m^2

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