Math Problem Statement

An Atwood's machine consists of blocks of masses

m1 = 12.0 kg

and

m2 = 22.0 kg

attached by a cord running over a pulley as in the figure below. The pulley is a solid cylinder with mass

M = 7.10 kg

and radius

r = 0.200 m.

The block of mass m2 is allowed to drop, and the cord turns the pulley without slipping. b)

What is the acceleration of the system, assuming the pulley axis is frictionless? (Give the magnitude of

a.)

m/s2

(c)

Find the tensions T1 and T2.

T1=  N T2=  N

Solution

To solve this problem, let's approach it in steps. We have an Atwood's machine where a pulley is involved with rotational inertia, and we need to consider the forces and torques acting on each component of the system.

Given dataTo solve this problem, let's approach it in steps. We have an Atwood's machine where a pulley is involved with rotational inertia, and we need to consider the forces and torques acting on each component of the system.

Given

  • m1=12.0kgm_1 = 12.0 \, \text{kg}
  • m2=22.0kgm_2 = 22.0 \, \text{kg}
  • Pulley mass M=7.10kgM = 7.10 \, \text{kg}
  • Pulley radius r=0.200mr = 0.200 \, \text{m}

Steps to Solution

  1. Define the forces:

    • The gravitational force on each mass:
      • Fg1=m1g=12.09.81=117.72NF_{g1} = m_1 \cdot g = 12.0 \cdot 9.81 = 117.72 \, \text{N}
      • Fg2=m2g=22.09.81=215.82NF_{g2} = m_2 \cdot g = 22.0 \cdot 9.81 = 215.82 \, \text{N}
    • Tension forces:
      • T1T_1 (tension in the cord connected to m1m_1)
      • T2T_2 (tension in the cord connected to m2m_2)
  2. Set up the equations of motion for m1m_1 and m2m_2:

    • For m1m_1: T1m1g=m1aT_1 - m_1 \cdot g = m_1 \cdot a
    • For m2m_2: m2gT2=m2am_2 \cdot g - T_2 = m_2 \cdot a
  3. Consider the rotational motion of the pulley:

    • The pulley’s rotational inertia I=12Mr2=127.10(0.200)2=0.142kgm2I = \frac{1}{2} M r^2 = \frac{1}{2} \cdot 7.10 \cdot (0.200)^2 = 0.142 \, \text{kg} \cdot \text{m}^2
    • The torque on the pulley due to the tensions is τ=T2rT1r\tau = T_2 \cdot r - T_1 \cdot r.
    • Using Newton's second law for rotation: τ=Iα\tau = I \cdot \alpha, where α\alpha is the angular acceleration.
    • Since a=αra = \alpha \cdot r, we can substitute α=ar\alpha = \frac{a}{r}, leading to (T2T1)r=Iar(T_2 - T_1) \cdot r = I \cdot \frac{a}{r}.
  4. Combine equations:

    • Substitute I=0.142kgm2I = 0.142 \, \text{kg} \cdot \text{m}^2: (T2T1)0.200=0.142a0.200(T_2 - T_1) \cdot 0.200 = 0.142 \cdot \frac{a}{0.200}
    • Simplify to get: T2T1=0.71aT_2 - T_1 = 0.71 \, a.
  5. Solve for aa:

    • From the equations for m1m_1 and m2m_2: T1=m1(g+a)andT2=m2(ga)T_1 = m_1 \cdot (g + a) \quad \text{and} \quad T_2 = m_2 \cdot (g - a)

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Classical Mechanics
Newton's Second Law
Rotational Motion
Torque

Formulas

Newton's Second Law: F = ma
Torque: τ = Iα
Rotational Inertia of Solid Cylinder: I = 0.5 * M * r^2
Angular Acceleration: α = a/r
Equations of Motion: T1 - m1 * g = m1 * a, m2 * g - T2 = m2 * a
Torque Equation for Pulley: (T2 - T1) * r = I * (a/r)

Theorems

Newton's Second Law
Rotational Dynamics Theorem

Suitable Grade Level

College Level (Undergraduate Physics)