Lesson_4.2_Homework_Solution

Lesson_4.2_Homework_Solution - Lesson 16 Homework Solutions...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lesson 16 Homework Solutions 1. A 2.5-kg cylinder of radius 11 cm is initially at rest. A rope of negligible mass is wrapped around it and pulled with a force of 17 N. Find (a) the torque exerted by the force, (b) the angular acceleration of the cylinder and (c) the angular velocity of the cylinder after 15 s. The torque arm is the radius of the cylinder. r = 0.11 m, F = 17 N (a) τ = r × F = 0.11 m × 17 N = 1.87 mN (b) The moment of inertia I of the cylinder is: I = ½ mr 2 = ½ × 2.5 × 0.11 2 = 0.015 kg m 2 4 kg 17 N 0.11 m τ = I α 2 -2 1.87 mN 0.015 k 124.7 ra g d s m I τ α == = (c) ω = ω i + α t = 0 + 124.7 rad s -2 × 15 s = 1870 rad s -1 2. A disk-shaped grindstone of mass 2.4 kg and radius 12 cm is spinning at 820 rpm. After the power is shut off, the grindstone comes to a stop in 12 s. (a) What is the angular acceleration of the grindstone? (b) What is the frictional torque responsible for stopping the grindstone? The moment of inertia I of the grindstone is: I = ½ mr 2 = ½ × 2.4 kg × (0.12 m) 2 = 0.017 kg m 2 (a) ω i = 820 rpm = 820 × 2 π / 60 = 85.9 rad s -1 -2 85.9 0 7.2 rad s 12 fo t ωω = = = (b) τ = I α = 0.017 kg m 2 × 7.2 rad s -2 = 0.12 mN 3. An external torque of 50 Nm is applied to a wheel mounted on an axle that is not frictionless. If the wheel attains an angular velocity of 720 rpm in 24 s, what is the moment of inertia of the wheel?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/01/2011 for the course PHY 2048 taught by Professor George during the Fall '10 term at Edison State College.

Page1 / 5

Lesson_4.2_Homework_Solution - Lesson 16 Homework Solutions...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online