Name:
Group Members
Momentum Summative Experiment
Aim : To estimate the muzzle velocities of two guns by applying conservation of
momentum to an inelastic collision. To use another technique to measure the velocity
to enable a comparison to be made.
Equipment available
Velcro tape (opposite types )
Stopwatch
Dart Guns (various types)
Balance
Masses
String, Blutack, metre rulers etc. as
required
Background :
If you catch a heavy ball while standing motionless on a skateboard, the momentum of
the ball is transferred to you and sets you in motion. If you measure your speed and
the masses of the ball, skateboard, and yourself, then you know the momentum of
everything after the ball is caught. But this is equal to the momentum of the ball
just before you caught it, from the law of conservation of momentum. To find the
speed of the ball before you caught it, divide the momentum by the mass of the ball.
A similar technique is used to determine the speed of high-speed bullets in the
laboratory.
A gun's muzzle velocity is the speed at which the projectile leaves the muzzle of the
gun. Muzzle velocities range from subsonic (below 330 ms-1) for some pistols to more
than 1,800 m·s-1 for tank guns firing kinetic energy penetrator ammunition. The latter
velocity is close to the limit achievable with chemical propellants.
Method
Keep a ‘journal’ of the methods you used to
try and determine the two muzzle velocities.
Be sure to include:
 all the modifications you make
during the course of the experiment
 reasons for making changes
 diagrams!
For this section I will be looking for your ability to recognise sources of error and
problem-solving. This is the major part of the practical – so do a good job of this.
Calculations
Include the working for your calculations to determine the muzzle velocity of two toy
guns. State any laws that you are using.
Discussion of Results
Do you think your results are accurate? Which of your final two methods do you
think would yield the most accurate results and why? What are the remaining
sources of error and what could you do to minimise them if you had more resources
(time/money)
Marks Scheme
Method Journal
Safety
Calculations
Accuracy of results
Discussion
TOTAL
Comments (Mr D’s)
9 marks
2 marks
4 marks
1 mark
4 marks
20 marks