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Linear Momentum

  • C7-51: BALLISTIC PENDULUM - PELLET GUN

    C7-51
    Determine the speed of an air gun pellet using a ballistic pendulum.
    The pellet from an air gun is shot into a foam-filled can, which acts as the pendulum. Conservation of linear momentum in the inelastic collision determines the speed with which the pendulum receptacle leaves the collision. Conservation of energy determines how high the pendulum will rise, or alternatively, the maximum angle to which it swings. Working backward, we can determine the velocity v of the pellet: v = [(M + m)/m] SQRT (2gh), where m is the mass of the pellet, M is the mass of the receptacle can, h is the height to which the can rises, and g is the acceleration of gravity. The height h is determined by measuring the radius R of the pendulum and the horizontal displacement x of the receptacle can after the collision. Be familiar with the safety mechanism, and know where the pellet exits the gun before firing. Pump gun ONCE before firing.

  • C7-52: BALLISTIC PENDULUM - LABORATORY MODEL

    C7-52
    Demonstrate operation of the standard laboratory type ballistic pendulum.
    A heavy ball is placed on the compressed spring, as shown in the photograph, and released by pulling the trigger. The ball fires into a catch on the bob of a physical pendulum, causing the bob to swing to a large angle, where it is caught by a ratchet system. Due to lack of time, this device is generally demonstrated only qualitatively during regular class lectures.
    OS1

  • C7-53: AIR TRACK - SPEED OF AIR GUN PELLET

    C7-53
    Determine the speed of an air gun pellet using conservation of momentum in an inelastic collision.
    The pellet is shot into a receptacle mounted on an air track glider. Conservation of momentum in the ensuing totally inelastic collision allows determination of the velocity v with which the pellet was shot: v = [(M+m)/m] V, where m is the mass of the pellet, M is the mass of the glider/receptacle, and V is the measured velocity with which the glider leaves the collision. The speed of the glider is determined using a photocell gate timer. Compare this result with the result from the standard ballistic pendulum demonstration using the air gun pellet, Demonstration C7-51. Pump the gun once only. Be familiar with the safety mechanism, and know where the pellet exits the gun before firing.

  • C8-22: ENERGY CONVERSION - SUPERBALL AND SOUNDING BOARD

    C8-22
    Show transformation of energy from one form to another.
    Observe that the rebound of the superball is less when it is dropped on the metal shelving than when it is dropped onto a hard surface such as the floor. Discuss the possible forms of energy involved. Do the same experiment with a ping pong ball; describe and explain any differences.

  • D1-30: TRAJECTORY FROM CIRCULAR ORBIT - OVERHEAD PROJECTOR

    D1-30
    Show that the instantaneous velocity of an object executing uniform circular motion is tangent to the circle.
    A marble is rolled around the inside of the circular band on an overhead projector. When the ball leaves the end of the circular segment it will travel in the direction tangent to the circle at the point where it leaves.

    A transparent sheet is available with an outline of the circle and various possible paths. This can be used to challenge the students to guess the outcome of the experiment before performing it.

    Compare D1-31 and D1-32, other demonstrations showing similar effects.
    D1

  • D1-31: TRAJECTORY FROM SPIRAL

    D1-31
    Show that forces are required to create circular motion.
    The apparatus pictured is positioned on a horizontal surface. A small ball bearing (in container at lower left of picture) is blown through the spiral hose, emerging at the right side and moving downward (in the picture), toward one of the five aluminum tube targets. Ask your students to predict: Which of the targets will it hit, and why?

    Consider using in conjunction with D1-30 or D1-32 to show the effect in a less complex scenario.
    OS10

  • D1-32: TRAJECTORY FROM CIRCULAR ORBIT

    D1-32
    Show that the instantaneous velocity of an object executing uniform circular motion is tangent to the circle.
    A pool ball is rolled clockwise around the inside of the circular band. When the ball leaves the end of the circular segment it will travel in the direction tangent to the circle at the point where it leaves. Consider placing tape markers on the table or floor and having students predict which direction it will go before performing the experiment. Have them justify their conclusions, then discuss the results afterwards.

    Compare D1-30 and D1-32, which show similar effects.
    D1