RP3: Determination Of G

Question 1

What is g?

Answer 1

Gravitational Field Strength

Question 2

What is meant by free-fall?

Answer 2

When the only force acting on an object is gravity

Question 3

What graph can be plotted from experimental data to determine g?

Answer 3

A graph of 2h/t against t

Question 4

Describe how an electromagnet system can be used to determine g

Answer 4

● magnetic ball bearing released by electromagnet clamped at known height
● timing system starts when electromagnet is switched off
● timer stops when ball lands on finish pad

Question 5

When using a clamp stand in this experiment, what safety precaution should be taken?

Answer 5

Clamo stand should have counterweight attached to stop it from toppling over

Question 6

What safety precaution should be taken when using an electromagnet?

Answer 6

Switch it off when not in use to minimise heating effect

Question 7

Suggest how light gates could be positioned to ensure that the ball falls directly through them

Answer 7

● use plumb line to demonstrate the expected path of the ball
● this allows the light gates to be positioned appropriately

Question 8

Why is it advantageous to use a small ball-bearing over a larger ball?

Answer 8

Air resistance on a small ball-bearing is negligible

Question 9

Why should there be a gap between the release position and the first light gate?

Answer 9

To ensure that the ball is moving quick enough when passing through the light gate

Question 10

Explain why the experiment would not be valid if the air resistance acting on the ball wasn’t negligible

Answer 10

The ball wouldn’t be in free-fall as the acceleration would not be purely due to the force of gravity

Question 11

Suggest why your obtained value of g may not be the same as the accepted value

Answer 11

● delays in the timing equipment (e.g. human reaction time)
● resistive forces may be significant
● errors in height measurements

Question 12

Would you expect your value of g to be greater or smaller than the accepted value?

Answer 12

Lower due to air resistance reducing downwards resultant force

Question 13

How could your results be improved?

Answer 13

Take repeat readings at each height and calculate the mean time.

Question 14

What is the advantage of using light gates over a stopclock in this experiment?

Answer 14

Results in a lower uncertainty in time measurements