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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Friction

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Friction

Consider the arrangement depicted in the figure. Determine the...

Consider the arrangement depicted in the figure. Determine the acceleration of the 1.0 kg1.0 \text{ kg} blocks. (Assume g=10 m/s2g = 10 \text{ m/s}^2)
Consider the arrangement depicted in the figure. Determine the acceleration of the 1.0 kg blocks. (Assume g = 10 m/s^2 )

Options

  1. A0.4 m/s20.4 \text{ m/s}^2
  2. B0.2 m/s20.2 \text{ m/s}^2
  3. C0.8 m/s20.8 \text{ m/s}^2
  4. D2.0 m/s22.0 \text{ m/s}^2

Correct answer

A. 0.4 m/s20.4 \text{ m/s}^2

Step-by-step solution

Let the masses of the blocks on the horizontal surface be m1=1.0 kgm_1 = 1.0 \text{ kg} and m2=1.0 kgm_2 = 1.0 \text{ kg}.

Let the mass of the hanging block be m3=0.5 kgm_3 = 0.5 \text{ kg}.

The driving force for the system is the weight of the hanging block:

Fdriving=m3g=0.5×10=5 NF_{\text{driving}} = m_3 g = 0.5 \times 10 = 5 \text{ N}

The frictional force opposing the motion acts on both blocks on the horizontal surface. The total frictional force is:

fk=μm1g+μm2g=μ(m1+m2)gf_k = \mu m_1 g + \mu m_2 g = \mu (m_1 + m_2) g

fk=0.2×(1.0+1.0)×10=4 Nf_k = 0.2 \times (1.0 + 1.0) \times 10 = 4 \text{ N}

Since the driving force (5 N5 \text{ N}) is greater than the total frictional force (4 N4 \text{ N}), the system will accelerate.

The net force acting on the system is:

Fnet=Fdriving−fk=5−4=1 NF_{\text{net}} = F_{\text{driving}} - f_k = 5 - 4 = 1 \text{ N}

The total mass of the system moving together is:

Mtotal=m1+m2+m3=1.0+1.0+0.5=2.5 kgM_{\text{total}} = m_1 + m_2 + m_3 = 1.0 + 1.0 + 0.5 = 2.5 \text{ kg}

The acceleration aa of the system is given by Newton's second law:

a=FnetMtotal=12.5=0.4 m/s2a = \dfrac{F_{\text{net}}}{M_{\text{total}}} = \dfrac{1}{2.5} = 0.4 \text{ m/s}^2
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