Newton's Cradle

Definition

Newton's cradle is a device that demonstrates the conservation of momentum and energy. It consists of a series of identical pendulums, usually metal balls, suspended from a frame in a line.

5 Must Know Facts For Your Next Test

1. When one ball at the end of the cradle is pulled and released, it collides with the next ball, causing the ball at the opposite end to swing outward.
2. The collisions between the balls demonstrate the transfer of kinetic energy and momentum from one ball to the next.
3. The height reached by the swinging ball is equal to the height from which the initial ball was released, illustrating the conservation of energy.
4. The motion of the balls in the cradle continues indefinitely, as long as no external forces (such as friction or air resistance) act on the system.
5. Newton's cradle is often used to illustrate the principle of action and reaction, as described in Newton's Third Law of Motion.

Review Questions

• Explain how Newton's cradle demonstrates the conservation of momentum.
  • In Newton's cradle, when one ball is pulled and released, it collides with the next ball. This collision causes the momentum of the initial ball to be transferred to the next ball, resulting in the ball on the opposite end of the cradle swinging outward. The total momentum of the system is conserved, as the momentum lost by the initial ball is gained by the next ball in the sequence.
• Describe how Newton's cradle illustrates the conservation of energy.
  • The conservation of energy is demonstrated in Newton's cradle by the fact that the height reached by the swinging ball on the opposite end is equal to the height from which the initial ball was released. This shows that the kinetic energy of the initial ball is converted to potential energy as it rises, and then back to kinetic energy as it swings back down. The total energy of the system remains constant, as energy is neither created nor destroyed, but rather transformed from one form to another.
• Analyze how Newton's cradle can be used to explain Newton's Third Law of Motion.
  • Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction, can be observed in the operation of Newton's cradle. When the initial ball collides with the next ball, the force exerted by the first ball on the second is equal in magnitude but opposite in direction to the force exerted by the second ball on the first. This action-reaction principle is demonstrated by the transfer of momentum and the resulting motion of the balls in the cradle, as the force applied to one ball is immediately transferred to the next, causing the ball on the opposite end to swing outward.

Related terms

Conservation of Momentum: The principle that the total momentum of a closed system is constant unless an external force acts on the system.

Conservation of Energy: The principle that the total energy of an isolated system remains constant, it is said to be conserved. It is said to be conserved, it is said to be conserved.

Pendulum: A weight suspended from a fixed point by a string or rod, which swings back and forth due to the force of gravity and momentum.