A Level Physics  

Calculating ‘g’ the force due to gravity using a pendulum.  

Welcome to A Level Physics!  Physics is all about explaining why things happen.  We all know that when you drop a ball it falls to the floor due to the gravitational force acting on it.  But what is the value of that gravitational force?  

In order to find out the value for ‘g’, the gravitational force on Earth, you can do a simple experiment, plot a graph and do a bit of maths.  (see how to plot graphs and work out errors attached).  Investigate other methods of finding g.  Which method is the best and why?  

This project will test your ability to conduct an experiment, draw a graph and interpret the results.  It will also give you an opportunity to develop your ability to reflect on your work and determine what you need to do to become even better than you currently are.  

Enjoy the task and remember to tell your friends how you were able to determine ‘g’, the gravitational force due to gravity with just a bit of blue tack, a piece of string and a watch.  

Equipment needed: 

• Something to tie a pendulum to.  

• Cotton or string.  

• Plasticine or some other small mass.  

• Stop clock or other timing device. 

• Graph paper  

Method  

• Attach the mass to one end of the string. • 

 Produce a pendulum of 0.1 m and release the pendulum and start the stop clock.   

• Calculate the time period, T, of the pendulum (the time it takes for the pendulum to complete 1 oscillation i.e. from left to right and back to the left again)  

• Repeat for pendulums of length 0.2m, 0.3m, 0.4m, 0.5m and 0.6m.  

• Plot a graph of T2 v L (length of the pendulum)  

• Work out the gradient of your graph.  

• Use the equation g = 4π2 / gradient to calculate the value of g.  

What you have to hand in!!  

In your first A Level Physics lesson, please hand in a report that includes:  

• Equipment  

• Method, including any risk assessments and what you did to minimise errors.  

• Results  

• Graph  

• Calculation of ‘g’  

• The actual value of g is 9.8 N/kg.  Compare your result with this.  

• Review your experiment and determine what went well and what you would do differently if you were to repeat it.    

Congratulations if you manage to complete the task ☺.

If you get stuck, all we ask is that you do your best and get as far as you can.  Just think that at the end of the year,  you will be able to do this and much more!!!!