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Ball B is suspended from a cord of length l attached to cart A, which can roll freely on a frictionless, horizontal track. The ball and the cart have the same mass m. If the cart is given an initial horizontal velocity v0 while the ball is at rest, describe the subsequent motion of the system, specifying the velocities of A and B for the following successive values of the angle θ (assume positive counterclockwise) that the cord will form with the vertical:

(a) θ = θmax
(b) θ = 0
(c) θ = θmin

User Kball
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2 Answers

6 votes

Final answer:

The motion involves energy conversion between kinetic and potential energy, with ball B reaching maximum potential energy at θmax and θmin, and maximum kinetic energy at θ = 0. Cart A's velocity will be adjusted according to the change in motion of ball B, based on the conservation of momentum.

Step-by-step explanation:

The question relates to the physics concept known as conservation of momentum and energy in the context of pendular motion and collisions within an isolated system. When cart A is given an initial velocity and ball B is at rest, the force that accelerates ball B will be the component of the tension in the string that acts horizontally, as there's no friction resistance on the track. During the motion, the total energy of ball B will be conserved, converting between potential energy when at its highest at θmax and θmin, and kinetic energy when passing through the lowest point at θ = 0. As the system consists of pendular motion, for a given displacement, the velocity of the pendulum and cart at various angles can be determined by using energy conservation.


  • (a) At θ = θmax, ball B is momentarily at rest, as it has reached its maximum height and thus its velocity is zero. All its energy is potential.

  • (b) At θ = 0, ball B passes through its lowest point, having maximum kinetic energy, and thus maximum velocity.

  • (c) At θ = θmin, similar to the case at θmax, ball B is momentarily at rest at its minimum height (which should be symmetric to the maximum height if air resistance is negligible), with all its energy being potential.

Given that cart A and ball B have the same mass, the velocities can be tracked by considering the movement as a combination of the cart rolling and the pendulum swinging, respecting the conservation of angular momentum around the axis from which the ball B is suspended.

User Kuljit
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5.3k points
4 votes

Answer:

a.Velocity of A and Velocity of B will be opposite in direction.

b.Both velocities have the same direction.

c. The two objects will move in a direction of some angle α.

Step-by-step explanation:

When the angle gets maximum the velocities of the two objects pull each other and move in opposite direction. But when the two objects make an angle zero degree with each other their motion is in the same direction.

User Maulik
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5.6k points