VECTOR MECH. FOR EGR: STATS & DYNAM (LL
VECTOR MECH. FOR EGR: STATS & DYNAM (LL
12th Edition
ISBN: 9781260663778
Author: BEER
Publisher: MCG
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Chapter 17, Problem 17.135RP

A uniform disk, initially at rest and of constant thickness, is placed in contact with the belt shown, which moves at a constant speed v = 80 ft/s. Knowing that the coefficient of kinetic friction between the disk and the belt is 0.15, determine (a) the number of revolutions executed by the disk before it reaches a constant angular velocity, (b) the time required for the disk to reach that constant angular velocity.

Chapter 17, Problem 17.135RP, A uniform disk, initially at rest and of constant thickness, is placed in contact with the belt

Fig. P17.135

(a)

Expert Solution
Check Mark
To determine

Find the number of revolutions executed by the disk before it reaches a constant angular velocity.

Answer to Problem 17.135RP

The number of revolutions executed by the disk is 106.7rev_.

Explanation of Solution

Given information:

The speed of the belt is v=80ft/s.

The coefficient of kinetic friction between the disk and the belt is μk=0.15.

The radius of the uniform disk is r=5in..

Calculation:

Show the free-body diagram of the disk as in Figure 1.

VECTOR MECH. FOR EGR: STATS & DYNAM (LL, Chapter 17, Problem 17.135RP , additional homework tip  1

Find the frictional force (Ff) using the relation.

Ff=μkN

Here, the normal force is N.

Substitute 0.15 for μk.

Ff=0.15N (1)

Resolve the vertical component of forces to find the normal force.

Fy=0Ncos25°Ffsin25°mg=0

Here, the mass of the disk is m and the acceleration due to gravity is g.

Consider the acceleration due to gravity as g=32.2ft/s2.

Substitute 0.15N for Ff.

Ncos25°0.15Nsin25°mg=00.90631N0.06339Nmg=0N=1.18635mg

Substitute 1.18635mg for N in Equation (1).

Ff=0.15(1.18635mg)=0.17795mg

Find the mass moment of inertia (I¯) using the equation.

I¯=12mr2

Here, the radius of the disk is r.

Find the angular velocity (ω2) using the relation.

ω2=vr

Find the work done (U12) applied in the process using the relation.

U12=Ffrθ

Here, the number of revolutions is θ.

Substitute 0.17795mg for Ff.

U12=0.17795mgrθ

The total kinetic energy at initial position is zero.

T1=0

Find the total kinetic energy after reaching the constant angular velocity using the relation.

T2=12I¯ω22

Substitute 12mr2 for I¯ and vr for ω2

T2=12(12mr2)(vr)2=mv24

Write the equation of conservation of energy and work as follows;

T1+U12=T2

Substitute 0 for T1, 0.17795mgrθ for U12, and mv24 for T2.

0+0.17795mgrθ=mv24

Substitute 5 in. for r, 32.2ft/s2 for g, and 80ft/s for v.

0.17795×32.2×5in.×1ft12in.×θ=8024θ=670.15824rad×1rev2πrad=106.7rev

Therefore, the number of revolutions executed by the disk is 106.7rev_.

(b)

Expert Solution
Check Mark
To determine

Find the time required for the disk to reach the constant angular velocity.

Answer to Problem 17.135RP

The time required for the disk is 6.98s_.

Explanation of Solution

Given information:

The speed of the belt is v=80ft/s.

The coefficient of kinetic friction between the disk and the belt is μk=0.15.

The radius of the uniform disk is r=5in..

Calculation:

Show the free-body diagram of the principle of impulse-momentum as in Figure 2.

VECTOR MECH. FOR EGR: STATS & DYNAM (LL, Chapter 17, Problem 17.135RP , additional homework tip  2

Take moment about point A as follows;

MA=I¯ω20+Fftr=I¯ω2

Substitute 0.17795mg for Ff, 12mr2 for I¯, and vr for ω2.

0.17795mgtr=12mr2vr0.17795gt=v2

Substitute 32.2ft/s2 for g and 80ft/s for v.

0.17795×32.2×t=802t=6.98s

Therefore, the time required for the disk is 6.98s_.

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Chapter 17 Solutions

VECTOR MECH. FOR EGR: STATS & DYNAM (LL

Ch. 17.1 - Prob. 17.6PCh. 17.1 - Prob. 17.7PCh. 17.1 - Prob. 17.8PCh. 17.1 - The 10-in.-radius brake drum is attached to a...Ch. 17.1 - Prob. 17.10PCh. 17.1 - Each of the gears A and B has a mass of 10 kg and...Ch. 17.1 - Solve Prob. 17.11, assuming that the 6 Nm couple...Ch. 17.1 - Prob. 17.13PCh. 17.1 - The double pulley shown has a mass of 15 kg and a...Ch. 17.1 - Gear A has a mass of 1 kg and a radius of gyration...Ch. 17.1 - A slender rod of length l and mass m is pivoted...Ch. 17.1 - The 15-kg rear hatch of a vehicle opens as shown...Ch. 17.1 - A slender 9-lb rod can rotate in a vertical plane...Ch. 17.1 - An adapted golf device attaches to a wheelchair to...Ch. 17.1 - A 10-kg storm window measuring 900 1500 mm is...Ch. 17.1 - A collar with a mass of 1 kg is rigidly attached...Ch. 17.1 - A collar with a mass of 1 kg is rigidly attached...Ch. 17.1 - Two identical slender rods AB and BC are welded...Ch. 17.1 - Prob. 17.24PCh. 17.1 - A 100-kg solid cylindrical disk, 800 mm in...Ch. 17.1 - Prob. 17.26PCh. 17.1 - Greek engineers had the unenviable task of moving...Ch. 17.1 - A small sphere of mass m and radius r is released...Ch. 17.1 - Prob. 17.29PCh. 17.1 - A half-cylinder with mass m and radius r is...Ch. 17.1 - Prob. 17.31PCh. 17.1 - Two uniform cylinders, each of weight W = 14 lb...Ch. 17.1 - Prob. 17.33PCh. 17.1 - A bar of mass m = 5 kg is held as shown between...Ch. 17.1 - The 1.5-kg uniform slender bar AB is connected to...Ch. 17.1 - The motion of the uniform rod AB is guided by...Ch. 17.1 - Prob. 17.37PCh. 17.1 - Prob. 17.38PCh. 17.1 - The ends of a 9-lb rod AB are constrained to move...Ch. 17.1 - The mechanism shown is one of two identical...Ch. 17.1 - The mechanism shown is one of two identical...Ch. 17.1 - Each of the two rods shown is of length L = 1 m...Ch. 17.1 - The 4-kg rod AB is attached to a collar of...Ch. 17.1 - If in Prob. 17.43 the angular velocity of the...Ch. 17.1 - The uniform rods AB and BC are of mass 3 kg and 8...Ch. 17.1 - The uniform rods AB and BC weigh 2.4 kg and 4 kg,...Ch. 17.1 - The 80-mm-radius gear shown has a mass of 5 kg and...Ch. 17.1 - Prob. 17.48PCh. 17.1 - Three shafts and four gears are used to form a...Ch. 17.1 - The experimental setup shown is used to measure...Ch. 17.1 - Prob. 17.51PCh. 17.2 - The 350-kg flywheel of a small hoisting engine has...Ch. 17.2 - Prob. 17.2IMDCh. 17.2 - Prob. 17.3IMDCh. 17.2 - Prob. 17.52PCh. 17.2 - A bolt located 2 in. from the center of an...Ch. 17.2 - A small grinding wheel is attached to the shaft of...Ch. 17.2 - A uniform 144-lb cube is attached to a uniform...Ch. 17.2 - Prob. 17.56PCh. 17.2 - Prob. 17.57PCh. 17.2 - Prob. 17.58PCh. 17.2 - Prob. 17.59PCh. 17.2 - Each of the double pulleys shown has a centroidal...Ch. 17.2 - Each of the gears A and B has a mass of 675 g and...Ch. 17.2 - Two identical uniform cylinders of mass m and...Ch. 17.2 - Two identical 16-lb uniform cylinders of radius r...Ch. 17.2 - Prob. 17.64PCh. 17.2 - Prob. 17.65PCh. 17.2 - Show that, when a rigid body rotates about a fixed...Ch. 17.2 - Prob. 17.68PCh. 17.2 - A flywheel is rigidly attached to a 1.5-in.-radius...Ch. 17.2 - A wheel of radius r and centroidal radius of...Ch. 17.2 - Prob. 17.71PCh. 17.2 - 17.72 and 17.73The 3-lb carriage C is supported as...Ch. 17.2 - Prob. 17.73PCh. 17.2 - Two uniform cylinders, each of mass m = 6 kg and...Ch. 17.2 - Prob. 17.75PCh. 17.2 - Prob. 17.76PCh. 17.2 - A sphere of radius r and mass m is projected along...Ch. 17.2 - A bowler projects an 8.5-in.-diameter ball...Ch. 17.2 - Prob. 17.79PCh. 17.2 - A satellite has a total weight (on Earth) of 250...Ch. 17.2 - Two 10-lb disks and a small motor are mounted on a...Ch. 17.2 - Prob. 17.82PCh. 17.2 - Prob. 17.83PCh. 17.2 - Prob. 17.84PCh. 17.2 - Prob. 17.85PCh. 17.2 - Prob. 17.86PCh. 17.2 - The 30-kg uniform disk A and the bar BC are at...Ch. 17.2 - Prob. 17.88PCh. 17.2 - A 1.8-kg collar A and a 0.7-kg collar B can slide...Ch. 17.2 - Prob. 17.90PCh. 17.2 - A small 4-lb collar C can slide freely on a thin...Ch. 17.2 - Rod AB has a weight of 6 lb and is attached to a...Ch. 17.2 - A 3-kg uniform cylinder A can roll without sliding...Ch. 17.2 - The 4-kg cylinder B and the 3-kg wedge A are at...Ch. 17.2 - The 6-lb steel cylinder A of radius r and the...Ch. 17.3 - A uniform slender rod AB of mass m is at rest on a...Ch. 17.3 - Prob. 17.5IMDCh. 17.3 - Prob. 17.6IMDCh. 17.3 - At what height h above its center G should a...Ch. 17.3 - A bullet weighing 0.08 lb is fired with a...Ch. 17.3 - In Prob. 17.97, determine (a) the required...Ch. 17.3 - A 16-lb wooden panel is suspended from a pin...Ch. 17.3 - Prob. 17.100PCh. 17.3 - A 45-g bullet is fired with a velocity of 400 m/s...Ch. 17.3 - A 45-g bullet is fired with a velocity of 400 m/s...Ch. 17.3 - The tire shown has a radius R = 300 mm and a...Ch. 17.3 - Prob. 17.104PCh. 17.3 - A uniform slender rod AB of mass m is at rest on a...Ch. 17.3 - A uniform slender rod AB is at rest on a...Ch. 17.3 - A bullet of mass m is fired with a horizontal...Ch. 17.3 - Determine the height h at which the bullet of...Ch. 17.3 - A uniform slender bar of length L = 200 mm and...Ch. 17.3 - A uniform slender rod of length L is dropped onto...Ch. 17.3 - A uniform slender rod AB has a mass m, a length L,...Ch. 17.3 - You have been hired to design a baseball catcher...Ch. 17.3 - The trapeze/lanyard air drop (t/LAD) launch is a...Ch. 17.3 - The uniform rectangular block shown is moving...Ch. 17.3 - The 40-kg gymnast drops from her maximum height of...Ch. 17.3 - A uniform slender rod AB of length L = 600 mm is...Ch. 17.3 - Prob. 17.118PCh. 17.3 - A 1-oz bullet is fired with a horizontal velocity...Ch. 17.3 - For the beam of Prob. 17.119, determine the...Ch. 17.3 - Prob. 17.121PCh. 17.3 - Prob. 17.122PCh. 17.3 - A slender rod AB is released from rest in the...Ch. 17.3 - Prob. 17.124PCh. 17.3 - Block A has a mass m and is attached to a cord...Ch. 17.3 - Prob. 17.126PCh. 17.3 - 17.127 and 17.128Member ABC has a mass of 2.4 kg...Ch. 17.3 - 17.127 and 17.128Member ABC has a mass of 2.4 kg...Ch. 17.3 - Prob. 17.129PCh. 17.3 - Prob. 17.130PCh. 17.3 - A small rubber ball of radius r is thrown against...Ch. 17.3 - Sphere A of mass m and radius r rolls without...Ch. 17.3 - In a game of pool, ball A is rolling without...Ch. 17 - A uniform disk, initially at rest and of constant...Ch. 17 - The 8-in.-radius brake drum is attached to a...Ch. 17 - A uniform slender rod is placed at corner B and is...Ch. 17 - The motion of the slender 250-mm rod AB is guided...Ch. 17 - A baseball attachment that helps people with...Ch. 17 - Disks A and B are made of the same material, are...Ch. 17 - Disks A and B are made of the same material, are...
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