A diametrical tunnel is dug across the earth. A ball is dropped into ...
Loss in potential energy = Gain in kinetic energy
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A diametrical tunnel is dug across the earth. A ball is dropped into ...
Given information:
- Gravitational potential at the center of the Earth = -3/2 GM/R
To find: Velocity of the ball when it reaches the center of the Earth
- Let's assume the radius of the Earth as R and the mass of the Earth as M.
- The gravitational potential energy at any point inside the Earth can be given by the formula U = -GMm/r, where G is the gravitational constant, m is the mass of the object, and r is the distance from the center of the Earth.
- As the ball is dropped from one side of the tunnel, it falls freely under the influence of gravity. Therefore, it will gain kinetic energy and lose potential energy.
- At the surface of the Earth, the potential energy of the ball is zero. As it falls towards the center, the potential energy decreases.
- At the center of the Earth, the potential energy is minimum and equal to -3/2 GM/R.
- According to the law of conservation of mechanical energy, the total mechanical energy of the ball remains constant throughout its motion.
- Therefore, at the surface of the Earth, the total mechanical energy of the ball is equal to its kinetic energy.
- At the center of the Earth, the total mechanical energy is equal to the kinetic energy plus the potential energy, which is -3/2 GM/R.
- Using the equation for kinetic energy (K.E. = 1/2 mv^2), we can equate the total mechanical energy at the surface to the kinetic energy at the center of the Earth.
- 1/2 mv^2 = -3/2 GM/R
- Simplifying the equation, we get v^2 = -3GM/R
- Taking the square root of both sides, we get v = √(3GM/R)
- Since g = GM/R, where g is the acceleration due to gravity, we can rewrite the equation as v = √(3gR)
- Therefore, the velocity of the ball when it reaches the center of the Earth is √(3gR), which is represented by option B.
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