In an experiment to verify the principle of conservation of momentum, a body A was set in motion with a constant velocity - Leaving Cert Physics - Question 1 - 2005

The time interval of 0.2 s was measured using a ticker tape timer. The timer works by printing dots at regular intervals. To measure 0.2 s:

1. Set up two light gates connected to a card on the trolley.
2. Calculate the time interval between the dots on the tape as 0.2 s (or 1/5 sec) based on the mechanism of the ticker tape.

(i) Before the collision: To find the velocity (v) of body A, we use the formula:
v = \frac{s}{t} = \frac{10.1 ext{ cm}}{0.2 ext{ s}} = 0.505 ext{ m s}^{-1} \approx 0.51 ext{ m s}^{-1}.

(ii) After the collision: Using the distance travelled after the collision: [ v = \frac{5.1 ext{ cm}}{0.2 ext{ s}} = 0.255 ext{ m s}^{-1} \approx 0.26 ext{ m s}^{-1} ]

To verify the principle of conservation of momentum, calculate the total momentum before and after the collision:

1. Before the collision:

   • Mass of body A: 520.1 g = 0.5201 kg
   • Distance travelled (s): 10.1 cm = 0.101 m
   • Momentum (p) of body A = m imes v = 0.5201 imes 0.505 = 0.263 ext{ kg m s}^{-1}.

2. After the collision:

   • Total mass after collision (combined mass of A and B): 520.1 g + 490.0 g = 1010.1 g = 1.0101 kg.
   • Velocity after collision = 0.255 m s^{-1}
   • Total momentum = 1.0101 imes 0.255 = 0.2576 ext{ kg m s}^{-1}.

The momenta before and after can be approximated to show conservation.

To minimize the effects of friction and gravity:

1. An air cushion or smooth surface was used to separate the track from direct contact (e.g., the air track).
2. The trolleys were equipped with wheels that offered minimal resistance.
3. The trolley was moved horizontally along the track with minimal incline, thus keeping gravitational effects minimal.