Two rigid bodies A and B rotate with rotational kinetic energies EAand...
Two rigid bodies A and B rotate with rotational kinetic energies EAand...
Given:
- Two rigid bodies A and B
- Rotational kinetic energies EA and EB
- Moments of inertia IA and IB
- IA = IB
- EA = 100 = EB
To find:
- The ratio of angular momentum LA of A to the angular momentum LB of B
**Solution:**
**Step 1: Understanding rotational kinetic energy and angular momentum**
- Rotational kinetic energy is the energy possessed by a rotating object due to its motion.
- It is given by the formula: KE = (1/2) Iω^2, where I is the moment of inertia and ω is the angular velocity.
- Angular momentum is a measure of the rotational motion of an object.
- It is given by the formula: L = Iω, where I is the moment of inertia and ω is the angular velocity.
**Step 2: Finding the relationship between rotational kinetic energy and angular momentum**
- We can rewrite the formulas for rotational kinetic energy and angular momentum as:
- KE = (1/2) Iω^2
- L = Iω
- Dividing the equation for angular momentum by the equation for rotational kinetic energy, we get:
- L/KE = (Iω) / ((1/2) Iω^2)
- L/KE = 2/ω
- This shows that the ratio of angular momentum to rotational kinetic energy is equal to 2 divided by the angular velocity.
**Step 3: Comparing the rotational kinetic energies and finding the ratio of angular momenta**
- Given that EA = 100 = EB, we can conclude that the rotational kinetic energies of A and B are equal.
- Since the rotational kinetic energy is the same for both bodies, the angular velocities ωA and ωB must also be the same.
- Therefore, the ratio of angular momenta LA/LB can be found using the equation L/KE = 2/ω:
- LA/EA = LB/EB
- LA/100 = LB/100
- LA = LB
- Therefore, the ratio of angular momentum LA of A to the angular momentum LB of B is 1:1 or 1.
**Step 4: Simplifying the ratio**
- Since the question asks for the ratio in terms of a fraction, we can simplify the ratio LA/LB = 1/1 as:
- LA/LB = 1/1 = 1
- Therefore, the ratio of angular momentum LA of A to the angular momentum LB of B is 1.
**Step 5: Identifying the correct option**
- Option (C) states that the ratio is 5, which is incorrect.
- Therefore, the correct answer is option (D) - 1/4.
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