Required Practicals

Question 1

Determining g from freefall method

Answer 1

• Measure h from the bottom of the ball bearing to the trap door
• Flick switch and start timer
• The ball bearing falls, knocking the trapdoor and breaking the circuit which stops the timer. Record T
• Repeat and drop the ball from different heights
• Plot graph (h against t^2)

Question 2

Errors in freefall experiment

Answer 2

• Most significant source of random error is the measurement of h (uncertainty of 1mm)
• using a small and heavy ball allows you to ignore resistance
• Having a computer automatically release and start the timer means a small uncertainty than if a human with a stop watch did it
• Doing it by hand gets large uncertainty due to human reaction times.
• Systematic error if there is a delay in the switch or timing mechanism

Question 3

Youngs Modulus method

Answer 3

• Test wire should be as thin and long as possible (reduces uncertainty)
• Find cross sectional area using a micrometer to measure diameter in several places. Use formula for area of a circle (pir^2)
• Clamp wire to bench so weights can be hung off one end, use weight to straighten wire but don’t measure it
• Measure distance from fixed end to marker
• increase weight to make the wire stretch
• Increase in 100g intervals
• Measure extension
• calculate stress and strain

Question 4

Problems with YM experiment

Question 5

Resistivity of a wire (202)

Question 6

e.m.f (209)

Question 7

mass-spring (238)

Question 8

Simple pendulum (241)

Question 9

Gas laws (257-259)

Question 10

Discharging through fixed resistor (315)

Question 11

Inverse square (376)

Question 12

Flux linkage (341)

Question 13

Force on a wire (330)