Math Problem Statement

A 12.0-kilogram box is on a horizontal surface. A pulley is attached to the right edge of the surface. A wire is attached to the box. The wire passes over the pulley and is attached to a hanging 5.00-kilogram weight. The x axis is directed horizontally to the right. The y axis is directed vertically upward. - A box on a horizontal surface is attached to a weight by a wire that passes over a pulley.

A 12.0 kg box resting on a horizontal, frictionless surface is attached to a 5.00 kg weight by a thin, light wire that passes over a frictionless pulley (Figure 1). The pulley has the shape of a uniform solid disk of mass 2.30 kg and diameter 0.500 m.

After the system is released, find the tension in the horizontal segment of the wire. Express your answer with the appropriate units.

After the system is released, find the tension in the vertical segment of the wire. Express your answer with the appropriate units.

After the system is released, find the x-component of the acceleration of the box. Express your answer with the appropriate units.

After the system is released, find the x- and y-components of the force that the axle exerts on the pulley. Express your answers in newtons separated by a comma.

Solution

To solve this problem, we need to analyze the forces and the motion in the system, considering the tension in the wire, the acceleration of the system, and the forces acting on the pulley.

Step 1: Define Variables and Given Information

  1. Mass of the box, m1=12.0kgm_1 = 12.0 \, \text{kg}
  2. Mass of the hanging weight, m2=5.00kgm_2 = 5.00 \, \text{kg}
  3. Mass of the pulley, M=2.30kgM = 2.30 \, \text{kg}
  4. Diameter of the pulley, D=0.500mD = 0.500 \, \text{m}, so radius R=0.250mR = 0.250 \, \text{m}

Since the surface is frictionless, and the pulley and wire are also frictionless, we will use Newton’s second law for both the box and the hanging weight, and rotational dynamics for the pulley.

Step 2: Set Up Equations of Motion

Box (horizontal motion)

The box has mass m1m_1 and experiences tension ThorizontalT_{\text{horizontal}} to the right. This tension will cause it to accelerate along the x-axis: m1a=Thorizontalm_1 \cdot a = T_{\text{horizontal}}

Hanging Weight (vertical motion)

The hanging weight experiences gravitational force m2gm_2 g downward and tension TverticalT_{\text{vertical}} upward. This force causes it to accelerate downward: m2gTvertical=m2am_2 g - T_{\text{vertical}} = m_2 \cdot a

Pulley (rotational motion)

The pulley has a rotational inertia I=12MR2I = \frac{1}{2} M R^2 and experiences a torque due to the tensions in the wire segments on each side (horizontal and vertical). The net torque on the pulley is given by: τ=Iα\tau = I \cdot \alpha where α=aR\alpha = \frac{a}{R} is the angular acceleration of the pulley. The torque generated by the tensions is: TverticalRThorizontalR=IαT_{\text{vertical}} \cdot R - T_{\text{horizontal}} \cdot R = I \cdot \alpha Substituting I=12MR2I = \frac{1}{2} M R^2 and α=aR\alpha = \frac{a}{R}, we get: TverticalThorizontal=12MaT_{\text{vertical}} - T_{\text{horizontal}} = \frac{1}{2} M \cdot a

Step 3: Solve for Tensions and Acceleration

1. Find the acceleration aa

Combine the three equations: m1a=Thorizontalm_1 a = T_{\text{horizontal}} m2gTvertical=m2am_2 g - T_{\text{vertical}} = m_2 a TverticalThorizontal=12MaT_{\text{vertical}} - T_{\text{horizontal}} = \frac{1}{2} M a Substitute Thorizontal=m1aT_{\text{horizontal}} = m_1 a from the first equation and rearrange the third equation to solve for TverticalT_{\text{vertical}}: Tvertical=m1a+12MaT_{\text{vertical}} = m_1 a + \frac{1}{2} M a Substitute this into the second equation: m2g(m1a+12Ma)=m2am_2 g - \left( m_1 a + \frac{1}{2} M a \right) = m_2 a Solve for aa: m2g=(m1+m2+12M)am_2 g = \left( m_1 + m_2 + \frac{1}{2} M \right) a a=m2gm1+m2+12Ma = \frac{m_2 g}{m_1 + m_2 + \frac{1}{2} M} Substitute the values: a=(5.00)(9.8)12.0+5.00+12(2.30)a = \frac{(5.00)(9.8)}{12.0 + 5.00 + \frac{1}{2} (2.30)} a=4913.153.725m/s2a = \frac{49}{13.15} \approx 3.725 \, \text{m/s}^2

2. Find the Tensions ThorizontalT_{\text{horizontal}} and TverticalT_{\text{vertical}}

  • Horizontal tension ThorizontalT_{\text{horizontal}}: Thorizontal=m1a=(12.0)(3.725)44.7NT_{\text{horizontal}} = m_1 \cdot a = (12.0)(3.725) \approx 44.7 \, \text{N}

  • Vertical tension TverticalT_{\text{vertical}}: Tvertical=m2gm2a=(5.00)(9.8)(5.00)(3.725)T_{\text{vertical}} = m_2 g - m_2 a = (5.00)(9.8) - (5.00)(3.725) [ T_{\text{vertical}} \approx 49 - 18.625 =

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Math Problem Analysis

Mathematical Concepts

Newton's Second Law
Rotational Dynamics
Torque

Formulas

Newton's Second Law: F = ma
Torque for rotational motion: τ = Iα
Moment of inertia for a solid disk: I = (1/2)MR^2

Theorems

Newton's Second Law
Rotational Dynamics Theorem

Suitable Grade Level

Grades 11-12