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To solve this problem, we need to determine the angular velocity of the rod at the instant \(\theta = 60^\circ\). We will use the principles of work and energy to solve this. ### Given: - Length of the rod, \( L = 2 \, \text{m} \) - Mass of the rod, \( m = 30 \, \text{kg} \) - Force applied, \( F = 40 \, \text{N} \) - Initial angle, \( \theta = 0^\circ \) - Final angle, \( \theta = 60^\circ \) - Neglect friction and the masses of blocks A and B. ### Steps to solve: 1. **Determine the work done by the force \( F \):** The work done by the force \( F \) as the rod moves from \(\theta = 0^\circ\) to \(\theta = 60^\circ\) can be calculated by considering the horizontal displacement of point B. When \(\theta = 0^\circ\), point B is at the origin. When \(\theta = 60^\circ\), the horizontal displacement \( x_B \) of point B is: \[ x_B = L \sin(60^\circ) = 2 \times \frac{\sqrt{3}}{2} = \sqrt{3} \, \text{m} \] The work done by the force \( F \) is: \[ W = F \cdot x_B = 40 \, \text{N} \times \sqrt{3} \, \text{m} = 40\sqrt{3} \, \text{J} \] 2. **Determine the change in potential energy:** The center of mass of the rod moves vertically as the rod rotates. Initially, when \(\theta = 0^\circ\), the center of mass is at a height of \( L/2 \) from the bottom. When \(\theta = 60^\circ\), the vertical height \( h \) of the center of mass is: \[ h = \frac{L}{2} \cos(60^\circ) = \frac{2}{2} \times \frac{1}{2} = \frac{1}{2} \, \text{m} \] The change in potential energy \( \Delta PE \) is: \[ \Delta PE = m g \Delta h = 30 \, \text{kg} \times 9.81 \, \text{m/s}^2 \times \left( \frac{1}{2} - 1 \right) \, \text{m} = 30 \times 9.81 \times \left( -\frac{1}{2} \right) = -147.15 \, \text{J} \] 3. **Apply the work-energy principle:** The work done by the force \( F \) is equal to the change in kinetic energy plus the change in potential energy: \[ W = \Delta KE + \Delta PE \] Since the rod starts from rest, the initial kinetic energy is zero. The final kinetic energy is: \[ \Delta KE = \frac{1}{2} I \omega^2 \] where \( I \) is the moment of inertia of the rod about the center of mass, and \( \omega \) is the angular velocity. For a rod rotating about its center, the moment of inertia \( I \) is: \[ I = \frac{1}{12} m L^2 = \frac{1}{12} \times 30 \, \text{kg} \times (2 \, \text{m})^2 = 10 \, \text{kg} \cdot \text{m}^2 \] Therefore: \[ 40\sqrt{3} = \frac{1}{2} \times 10 \times \omega^2 - 147.15 \] Solving for \(\omega\): \[ 40\sqrt{3} + 147.15 = 5 \omega^2 \] \[ 69.28 + 147.15 = 5 \omega^2 \] \[ 216.43 = 5 \omega^2 \] \[ \omega^2 = \frac{216.43}{5} = 43.286 \] \[ \omega = \

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To solve this problem, we need to determine the angular velocity of the rod at the instant θ=60\theta = 60^\circ. We will use the principles of work and energy to solve this. ### Given: - Length of the rod, L=2m L = 2 \, \text{m} - Mass of the rod, m=30kg m = 30 \, \text{kg} - Force applied, F=40N F = 40 \, \text{N} - Initial angle, θ=0 \theta = 0^\circ - Final angle, θ=60 \theta = 60^\circ - Neglect friction and the masses of blocks A and B. ### Steps to solve: 1. Determine the work done by the force F F : The work done by the force F F as the rod moves from θ=0\theta = 0^\circ to θ=60\theta = 60^\circ can be calculated by considering the horizontal displacement of point B. When θ=0\theta = 0^\circ, point B is at the origin. When θ=60\theta = 60^\circ, the horizontal displacement xB x_B of point B is: xB=Lsin(60)=2×32=3m x_B = L \sin(60^\circ) = 2 \times \frac{\sqrt{3}}{2} = \sqrt{3} \, \text{m} The work done by the force F F is: W=FxB=40N×3m=403J W = F \cdot x_B = 40 \, \text{N} \times \sqrt{3} \, \text{m} = 40\sqrt{3} \, \text{J} 2. Determine the change in potential energy: The center of mass of the rod moves vertically as the rod rotates. Initially, when θ=0\theta = 0^\circ, the center of mass is at a height of L/2 L/2 from the bottom. When θ=60\theta = 60^\circ, the vertical height h h of the center of mass is: h=L2cos(60)=22×12=12m h = \frac{L}{2} \cos(60^\circ) = \frac{2}{2} \times \frac{1}{2} = \frac{1}{2} \, \text{m} The change in potential energy ΔPE \Delta PE is: ΔPE=mgΔh=30kg×9.81m/s2×(121)m=30×9.81×(12)=147.15J \Delta PE = m g \Delta h = 30 \, \text{kg} \times 9.81 \, \text{m/s}^2 \times \left( \frac{1}{2} - 1 \right) \, \text{m} = 30 \times 9.81 \times \left( -\frac{1}{2} \right) = -147.15 \, \text{J} 3. Apply the work-energy principle: The work done by the force F F is equal to the change in kinetic energy plus the change in potential energy: W=ΔKE+ΔPE W = \Delta KE + \Delta PE Since the rod starts from rest, the initial kinetic energy is zero. The final kinetic energy is: ΔKE=12Iω2 \Delta KE = \frac{1}{2} I \omega^2 where I I is the moment of inertia of the rod about the center of mass, and ω \omega is the angular velocity. For a rod rotating about its center, the moment of inertia I I is: I=112mL2=112×30kg×(2m)2=10kgm2 I = \frac{1}{12} m L^2 = \frac{1}{12} \times 30 \, \text{kg} \times (2 \, \text{m})^2 = 10 \, \text{kg} \cdot \text{m}^2 Therefore: 403=12×10×ω2147.15 40\sqrt{3} = \frac{1}{2} \times 10 \times \omega^2 - 147.15 Solving for ω\omega: 403+147.15=5ω2 40\sqrt{3} + 147.15 = 5 \omega^2 69.28+147.15=5ω2 69.28 + 147.15 = 5 \omega^2 216.43=5ω2 216.43 = 5 \omega^2 ω2=216.435=43.286 \omega^2 = \frac{216.43}{5} = 43.286 [ \omega = \

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Solution

The square root of 43.286, which gives us the angular velocity ω \omega , is approximately 6.58 rad/s. Therefore, the angular velocity of the rod at the instant ( \theta = 60^\

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To solve this problem, we need to determine the angular velocity of the rod at the instant \(\theta = 60^\circ\). We will use the principles of work and energy to solve this. ### Given: - Length of the rod, \( L = 2 \, \text{m} \) - Mass of the rod, \( m = 30 \, \text{kg} \) - Force applied, \( F = 40 \, \text{N} \) - Initial angle, \( \theta = 0^\circ \) - Final angle, \( \theta = 60^\circ \) - Neglect friction and the masses of blocks A and B. ### Steps to solve: 1. **Determine the work done by the force \( F \):** The work done by the force \( F \) as the rod moves from \(\theta = 0^\circ\) to \(\theta = 60^\circ\) can be calculated by considering the horizontal displacement of point B. When \(\theta = 0^\circ\), point B is at the origin. When \(\theta = 60^\circ\), the horizontal displacement \( x_B \) of point B is: \[ x_B = L \sin(60^\circ) = 2 \times \frac{\sqrt{3}}{2} = \sqrt{3} \, \text{m} \] The work done by the force \( F \) is: \[ W = F \cdot x_B = 40 \, \text{N} \times \sqrt{3} \, \text{m} = 40\sqrt{3} \, \text{J} \] 2. **Determine the change in potential energy:** The center of mass of the rod moves vertically as the rod rotates. Initially, when \(\theta = 0^\circ\), the center of mass is at a height of \( L/2 \) from the bottom. When \(\theta = 60^\circ\), the vertical height \( h \) of the center of mass is: \[ h = \frac{L}{2} \cos(60^\circ) = \frac{2}{2} \times \frac{1}{2} = \frac{1}{2} \, \text{m} \] The change in potential energy \( \Delta PE \) is: \[ \Delta PE = m g \Delta h = 30 \, \text{kg} \times 9.81 \, \text{m/s}^2 \times \left( \frac{1}{2} - 1 \right) \, \text{m} = 30 \times 9.81 \times \left( -\frac{1}{2} \right) = -147.15 \, \text{J} \] 3. **Apply the work-energy principle:** The work done by the force \( F \) is equal to the change in kinetic energy plus the change in potential energy: \[ W = \Delta KE + \Delta PE \] Since the rod starts from rest, the initial kinetic energy is zero. The final kinetic energy is: \[ \Delta KE = \frac{1}{2} I \omega^2 \] where \( I \) is the moment of inertia of the rod about the center of mass, and \( \omega \) is the angular velocity. For a rod rotating about its center, the moment of inertia \( I \) is: \[ I = \frac{1}{12} m L^2 = \frac{1}{12} \times 30 \, \text{kg} \times (2 \, \text{m})^2 = 10 \, \text{kg} \cdot \text{m}^2 \] Therefore: \[ 40\sqrt{3} = \frac{1}{2} \times 10 \times \omega^2 - 147.15 \] Solving for \(\omega\): \[ 40\sqrt{3} + 147.15 = 5 \omega^2 \] \[ 69.28 + 147.15 = 5 \omega^2 \] \[ 216.43 = 5 \omega^2 \] \[ \omega^2 = \frac{216.43}{5} = 43.286 \] \[ \omega = \

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