Product Instructions: ‘g’ by Free Fall
FO71755
Apparatus
This apparatus is a complete solution for measuring ‘g’ by free fall accurately and reliably.
The release mechanism is a solenoid with switch, which when turned off, releases a metallic
ball. Connections on the top allow the unit to be connected to the trigger of the timer, so the
timer starts as soon as the ball is released.
The drop table has a sensor which detects the ball landing, and can be electrically connected
to the stop trigger of the timer, so as soon as the ball lands, the timer stops.
The timer has 1ms precision, so the drop time of the ball can be measured precisely, and the
trigger inputs ensure the measurements are accurate and repeatable.
Setup
See the last page for a setup diagram.
The release mechanism should be mounted on a retort rod, with the 4mm sockets pointing up,
at a height of 1m.
The table with the microswitch should be placed directly underneath the release mechanism.
Connect the power supply to the red and black sockets on the release mechanism, but do not
turn on the power supply yet.
Connect the yellow and blue sockets of the release mechanism to the START input of the timer.
Connect the blue and yellow sockets on the table to the STOP input of the timer.
Switch on the power supply, and ensure the power switch on the release mechanism is turned
on. When turned on, the ball bearing will attach to and be held by the electromagnet of the
release mechanism.
Measure the distance between the ball bearing, as it is held by the release mechanism, and the
table. Adjust the height of the release mechanism such that the distance is 1 metre.
www.timstar.co.uk science@timstar.co.uk
01270 250459 01270 250601
Product Instructions: ‘g’ by Free Fall
Theory
Consider the equation of motion:
s: distance
s = ut + 12– at2
a: acceleration
u: starting velocity
If an object is released at a height, then its starting velocity . The acceleration is simply
acceleration under gravity, a = g.
Therefore, if the distance s is known, then the equation can be rearranged to find g:
2s
g=–
t2
Experiment
Turn on the power to the release mechanism, and place the ball bearing so it is held by the
electromagnet.
Turn on the timer and ensure it is set to zero (press reset if it does not read zero).
Switch of the power to the release mechanism using the switch. This will release the ball bearing
and start the timer simultaneously.
When the ball bearing lands on the table, the timer will stop.
Use the time measured to determine a value for g. Remember that the time is in milliseconds,
so divide by 1000 to get a value in seconds.
Try repeating the experiments using different heights. Does the result change? What effect does
this have on the accuracy?
www.timstar.co.uk science@timstar.co.uk
01270 250459 01270 250601
Product Instructions: ‘g’ by Free Fall
www.timstar.co.uk science@timstar.co.uk
01270 250459 01270 250601