Higher Physics
Mechanics : Dynamics
Practical Activity Guide Booklet
ACTIVITY DYN 1
Title: Lifts
Aim: To calculate the acceleration of a lift.
Apparatus: 1 set of bathroom scales
Instructions
 Use the scales to determine your weight in newtons (N) and your
mass in kilograms (kg).
 Stand on the scales inside the lift and note the reading on the
scales while the lift is stationary.
 Press the button to send the lift upwards.
Note:
a) the maximum reading on the scales as the lift accelerates upwards
b) the reading on the scales as the lift is travelling at a constant speed
c) the minimum reading on the scales as the lift decelerates to a halt.
Repeat the experiment for the downwards journey of the lift.
Use the results to calculate the acceleration of the lift at the three
stages of each journey.
ACTIVITY DYN 2
Title: Work done
Aim: To calculate the work done by the force of friction acting on a
trolley moving down a slope.
Apparatus: 1 light gate & timer, 1 trolley with card, 1 runway / slope, 1
metre stick, scales.
INSTRUCTIONS
Measure the mass of the trolley, m.
Set up the apparatus as shown, marking the initial position of the centre
of the trolley on the slope.
Measure the distance, d, travelled by the trolley to the light gate.
Release the trolley, allowing it to run through the light beam.
Note the time recorded on the timer at the light gate and calculate the
speed of the trolley, v, through the light gate.
Measure the difference in height between the starting position and the
position of the light gate; height h.
Calculate the loss in gravitational potential energy of the trolley.
Calculate the gain in kinetic energy of the trolley.
Hence calculate the energy “difference” due to friction.
By considering the work done by friction on the trolley, calculate the
average force of friction acting on the trolley over the distance, d, down
the runway.
Extension
By considering the uncertainties in the measured quantities in the above experiment,
estimate a value for the absolute uncertainty in the average force of friction for the
journey.
ACTIVITY DYN 3 A
Title: Conservation of momentum
Aim: To compare the total momentum before and after a collision.
Apparatus: 1 linear air track, 2 vehicles with cards, 2 light gates, 1
computer & velocity software, scales.
Instructions
Note the masses of vehicle A and vehicle B.
Set the computer to measure 3 velocities.
Keeping vehicle B stationary, push A towards B.
Note: a) the velocity of A through light gate 1
b) the velocity of B through light gate 2
c) the velocity of A through light gate 1 or 2 (if at all!).
Compare the total momentum before and after the collision.
Repeat the experiment for different masses of vehicle A and vehicle B.
Use an appropriate format to compare the total momentum before and
after the collision.
ACTIVITY DYN 3 B
Title: Explosions
Aim: To compare the total momentum before and after a collision using
explosive trolleys.
Apparatus: 2 trolleys with cards, 2 light gates, 1 computer & velocity
software, scales.
Instructions
Note the masses of trolleys A and B .
Set the computer to measure two velocities.
With both trolleys stationary, strike the plunger.
Note:
a) the velocity of A through light gate 1
b) the velocity of B through light gate 2.
Compare the total momentum before and after the explosion.
(Remember momentum is a vector quantity).
Repeat the experiment for different masses of trolleys.
ACTIVITY DYN 4A
Title: Impulse
Aim: To calculate average force exerted by a “putter” on a golf ball.
Apparatus: 1 “putter” and mountings, 1 metal painted golf ball with metal
“tee,” 1 light gate, 2 millisecond timers, scales
Instructions
Measure the mass of the golf ball, m, and the diameter of the golf ball.
Reset both millisecond timers to zero.
Place the light gate in front of the ball so that it will pass through the
centre of the beam after having been struck by the “putter” head.
Pull the “putter” head back and allow it to strike the ball.
Note the time of contact on timer 1.
Using the time recorded on millisecond timer 2, calculate the velocity, v,
of the golf ball after being struck by the “putter” head.
Use the equation Ft = mv - mu to calculate the force acting on the ball.
ACTIVITY DYN 4 B
Title: Impulse
Aim: To compare different times of contact for different balls bouncing
on a hard surface.
Apparatus: 3 balls of different types, covered in metal foil, 1 retort
stand,1 millisecond timer
Instructions
Reset the millisecond timer to zero.
Raise the first ball to a set height h, e.g. 50 cm, and allow it to bounce
once only onto the retort stand base.
Note down the time, t, recorded on the millisecond timer. This is the time
of contact between the ball and the retort stand base during the bounce.
Repeat 3 or 4 times from the same height and obtain an average value for
the time.
Repeat the experiment for the other two balls, dropping them from the
same height.
Below are three examples of force-time graphs, showing force varying
with time.
From the results of your experiment, match the ball used to the graph
that could show the variation of force with time during the bounce.
By considering the materials the balls are made from, explain the results.
ACTIVITY DYN 4 C
Title: Impulse
Aim: To compare force-time graphs for different collisions.
Apparatus: Pasco interface, motion sensor, force sensor, track, bumper,
computer.
Instructions
Set up the computer to plot graphs of :a) force against time
b) velocity against time.
Give the trolley a gentle push so it collides with the bumper.
Use the statistics function to calculate the area under the force - time
graph for the first collision.
Read off the velocity before and after the collision.
Measure the mass of the trolley and hence calculate the change of
momentum.
Compare this with the impulse calculated (area under the graph).
Account for any difference.
Repeat the experiment with a slightly stronger push.
Explain any differences in the graphs produced.
Now replace the spring with clay and repeat the process.
Explain the change in the shape of the force-time graph.
ACTIVITY 4D
Repeat Activity 16A using repelling magnets between the trolley and
bumper.