Math Problem Statement

Skip mo na to. A box with mass M=M= 14.3 [kg] is placed on a rough surface with coefficient of kinetic friction of 0.245. The mass is attached to two balls m1m1 and m2=m2= 10.6 [kg] via two pieces of rope and the system starts sliding as shown. The rope slides around the pulley mechanism frictionlessly. Given that the first rope exerts a tension force of 112 [N] on both the box and m1m1, what is the mass of m1m1?

Solution

Let's break down the problem into simpler steps using Newton's second law, F=maF = ma, where FF is the force, mm is the mass, and aa is the acceleration.

Key information provided:

  • Mass of the box, M=14.3kgM = 14.3 \, \text{kg}.
  • Coefficient of kinetic friction, μk=0.245\mu_k = 0.245.
  • Tension in the first rope, T1=112NT_1 = 112 \, \text{N}.
  • Mass of the second ball, m2=10.6kgm_2 = 10.6 \, \text{kg}.

We need to find the mass of m1m_1.

Step 1: Forces on the box

Since the box is sliding on a rough surface, the forces acting on the box in the horizontal direction are:

  • Tension T1T_1 pulling the box to the right.
  • Kinetic friction force fkf_k, which opposes the motion.

The kinetic friction force is given by: fk=μkNf_k = \mu_k \cdot N where NN is the normal force. Since the box is on a horizontal surface, the normal force is equal to the gravitational force on the box: N=Mg=14.3kg9.81m/s2=140.283N.N = M \cdot g = 14.3 \, \text{kg} \cdot 9.81 \, \text{m/s}^2 = 140.283 \, \text{N}. Thus, the kinetic friction force is: fk=0.245140.283=34.859N.f_k = 0.245 \cdot 140.283 = 34.859 \, \text{N}.

Step 2: Net force on the box

The net force acting on the box is the difference between the tension in the rope and the kinetic friction: Fnet, box=T1fk=112N34.859N=77.141N.F_{\text{net, box}} = T_1 - f_k = 112 \, \text{N} - 34.859 \, \text{N} = 77.141 \, \text{N}. Using Newton’s second law, the net force is also equal to the mass of the box multiplied by its acceleration: Fnet, box=Ma.F_{\text{net, box}} = M \cdot a. Thus, the acceleration of the box is: a=Fnet, boxM=77.141N14.3kg=5.394m/s2.a = \frac{F_{\text{net, box}}}{M} = \frac{77.141 \, \text{N}}{14.3 \, \text{kg}} = 5.394 \, \text{m/s}^2.

Step 3: Forces on m1m_1

Now, consider the forces acting on m1m_1. The forces are:

  • The gravitational force on m1m_1, which is m1gm_1 \cdot g.
  • The tension T1T_1 acting upward.

Using Newton's second law for m1m_1, we have: m1gT1=m1a.m_1 \cdot g - T_1 = m_1 \cdot a. Rearranging this equation to solve for m1m_1: m1gm1a=T1m_1 \cdot g - m_1 \cdot a = T_1 m1(ga)=T1m_1 \cdot (g - a) = T_1 m1=T1ga=112N9.81m/s25.394m/s2.m_1 = \frac{T_1}{g - a} = \frac{112 \, \text{N}}{9.81 \, \text{m/s}^2 - 5.394 \, \text{m/s}^2}. m1=1124.416=25.37kg.m_1 = \frac{112}{4.416} = 25.37 \, \text{kg}.

Thus, the mass of m1m_1 is approximately 25.4 kg.

Would you like further clarification or details?

Here are 5 related questions to explore:

  1. How would changing the coefficient of kinetic friction affect the system’s acceleration?
  2. What happens to the acceleration if m1m_1 is increased by 10%?
  3. How would the system behave if the surface were frictionless?
  4. How does the tension in the rope compare with the gravitational force on m2m_2?
  5. What would happen if the pulley had friction?

Tip: Always check if the forces are balanced properly when dealing with multiple objects in motion.

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Math Problem Analysis

Mathematical Concepts

Newton's Second Law
Kinetic Friction
Tension in a Rope
Gravitational Force

Formulas

Newton's Second Law: F = ma
Kinetic Friction: f_k = μ_k * N
Net Force: F_net = T - f_k
Gravitational Force: F = m * g

Theorems

Newton's Second Law

Suitable Grade Level

Grades 10-12