# Level 3 Physics

Conical Pendulum practical

Example of what year 13 Physics get up to!

Conducted by Caitlin, Jasmine and William

On Friday our Level 3 Physics class made a trip down to Kennedy Park to conduct a practical on a life sized pendulum. We placed our testee, Josh Keen, on to the rope swing and swung him in a circle to create a conical pendulum. The reason for our investigation was to find the size of the gravity acting on him as he swung (our only restriction was that we weren't allowed to use gravity in any of our formulas).

To start the practical we measured the mass of Josh, the length of the rope and the radius of the circle he was spinning. We recorded the average time for 1 oscillation by timing 5 reps of 3 oscillations, recording the average for this then dividing that number by 3. Using the formula F=MA and Ac=v2r we calculated Fc after calculating the horizontal velocity of Josh. We knew that v=d/t and distance was the distance around the bottom of the conical shape made by swinging (circle) using our knowledge of the radius already measured. From this we calculated the circumference of the circle. After calculating the circumference we were able to use the measurement to work out Josh’s horizontal velocity. Using our calculation of Ac (centripetal acceleration) we were able to calculate Fc (centripetal force). This then allowed us to calculate the weight force after using pythagoras theorem to work out the angle between the pole and the rope attached. Now knowing the weight force, along with the knowledge of Josh’s mass we could work out the value of gravity acting on Josh (Fw=Mg).

If we were to conduct this experiment again we would use different measurement techniques to help improve our accuracy.

Josh might also want to go for more runs because 60 kg is huge!