Core Practical 16: Investigating Resonance

Question 1

CP16 Equipment List

Answer 1

• Spring
• 100g masses and hanger
• Clamp stand and clamp
• Digital timer
• Unknown test mass
• Digital scales

Question 2

CP16 Method

Answer 2

• Hang number of masses to end of spring
• Extend spring up to position of fiducial marker, release and start stopwatch
• Measure time for 10 oscillations; find T by /10
• Repeat several times and find mean T
• Vary number of masses and record T for each oscillation
• Plot T² against mass
• Attach unknown mass to end of spring and record T
• Use graph to calculate value of mass

Question 3

CP16 Safety

Answer 3

Clamp stand
- Clamp stand to desk to prevent it falling
Overload spring
- Don’t overload spring so it doesn’t break and cause harm

Question 4

How to reduce uncertainty CP16?

Answer 4

More oscillations
- More oscillations reduces % uncertainty
Fiducial marker closer to equilibrium position
- velocity high near equilibrium; uncertainty in starting/stopping the stopwatch is least
Use video analysis
- Easier to replay and pinpoint when mass passes fiducial marker

Question 5

Describe method used could be improved to determine more accurate value of time period

Answer 5

• Take several oscillation and divide calculated time for the oscillation by this number
• Repeat measurements and calculate mean to reduce effect of errors
• Use fiducial marker
• At equilibrium position/ centre

Question 6

Explain why amplitude of oscillation of pendulum doesn’t stay consistent if air resistance is present

Answer 6

• Resistive forces present
• Transfers energy away from system
• Reduces max energy/amplitude of its oscillation

Question 7

Potential errors in CP16

Answer 7

• Difficult to measure from same position on spring each time
• Ruler may move in between readings
• Potential parallax error in reading positions
• Take more measurements of each mass

Question 8

Ways to improve accuracy of CP16

Answer 8

• Take measurements from mass holder
• Bring metre ruler closer to spring
• Use multiple measurements to calculate mean for each mass
• Ensure metre ruler is straight using set square
• Take reading at eye level to reduce parallax error

Question 9

Comment on use of data logger and light gates to measure time

Answer 9

• Data logger removes effect of human reaction; reduce uncertainty in measurement of time
• Not easy to measure timings for multiple oscillations using data logger

Question 10

Potential systematic error

Answer 10

Ignoring mass of holder/spring