Gravity by Time of Flight

<Previous | Next>

Distance travelled by a freely falling body is given by the equation $ S = \frac{1}{2}gt^2 => g=\frac{2S}{t^2}$. A mild steel ball is attached to an electromagnet fixed at a height. A contact sensor is kept below. The ball is releasd under program control and the time to reach the contact sensor is measured. The experimental setup is shown below.

The distance from the lowermost point to the contact sensor is 27 cm. Using the equation $ g = \frac{2S}{t^2} = \frac{54}{0.2354^2} = 974.5 . The value of ā€˜gā€™ is very close to the actual value but there are several sources of error.

The Python program to perform this experiment is listed below.

import eyes17.eyes
p = eyes17.eyes.open()

S = 27     # height

for k in range(5):
	p.set_state(OD1 =0)			# The relay used is energized when control voltage is LOW.
	input('Attach the ball and press the Enter key')
	res = p.set2ftime('OD1', 'SEN')		# SEN goes LOW when the ball hits the sensor.
	res -= 0.003  # 3 mS delay in releasing the ball
	print(res, 2*S/res**2)