Experiment # P205 General College Physics I

Dr. Ahmad Ballistic Pendulum Date:________

Name:_________________________

Group Names:______________________________________

Object: To determine the velocity of a projectile by means of a ballistic pendulum apparatus.

Apparatus: Ballistic pendulum apparatus, steel ball, balance and measuring tape.

Theory:

Fig.1. Bullet of mass m colliding with a Ballistic pendulum of mass M

1. A bullet of mass m travelling with a velocity V in the x-direction strikes the Ballistic pendulum of mass M initially at rest.

2. Just after the collision in which the bullet is captured by the pendulum, the velocity of the two together is V₁.

3. According to conservation of momentum

mV = (m + M) V₁ ……… (1)

4. The bullet-pendulum combination originally at a height Y₁ rises to a height Y₂ above the reference level shown. Kinetic energy is not conserved in this collision. However, the kinetic energy of the bullet-pendulum combination is converted to the potential energy when it rises to a height of (Y₂ - Y₁). Then

(1/2)(m + M)V₁² = (m + M).g.(Y₂ - Y₁) ……(2)

5. Solving (1) and (2) we get:

V₁ = Ö (2g (Y₂ - Y₁)) and V = (m + M)V₁ / m

Procedure:

(a) Ballistic Pendulum:

1. Slide the projectile ball onto the rod of the spring gun. Measure Y_1, the height of the center of the ball above the base of the apparatus. Cock the gun by pushing against the ball until the latch catches.

2. Fire the ball into the stationary pendulum.

3. The pendulum will swing up and then lodge in the notched track. Measure the distance Y₂ of the center of the ball above the base of the apparatus.

4. Repeat the above procedure for a total of five trials.

Observations:

Mass of bullet m =

Mass of pendulum assembly M =

TABLE I Ballistic pendulum

Trials	Y1 m	Y2 m	Velocity V1 m/s	Velocity V m/s
1.
2.
3.
4.
5.

Calculations: Complete the last two columns of the table.

Result: Report your results in a brief statement.

Sources of Error: Write down the sources of error in this experiment.