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A student used the apparatus shown to investigate circular motion - Edexcel - A-Level Physics - Question 2 - 2023 - Paper 6
Question 2
A student used the apparatus shown to investigate circular motion. The rubber bung with mass M was rotated around the plastic tube at a constant angular velocity $ ... show full transcript
Worked Solution & Example Answer:A student used the apparatus shown to investigate circular motion - Edexcel - A-Level Physics - Question 2 - 2023 - Paper 6
Step 1
Show that the relationship between the period of rotation T and mass M can be written as:
Answer
To derive the relationship, start with the equation of motion associated with circular motion:
u^2 / r$$ Given that the tension in the string provides the required centripetal force, we equate this to the weight of the mass under gravity, so: $$Mg = m u^2$$ Now, we know the relationship between angular velocity and the period is given by:u = \frac{2\pi}{T}Mg = m \left(\frac{2\pi}{T}\right)^2T^2 = \frac{4\pi^2 m}{Mg}$$
Step 2
Devise a plan to test the validity of the relationship between T^2 and M.
Answer
- Use a timing marker to mark the start and end of a rotation.
- Start timing after a few rotations.
- Time a number of rotations and divide by the number of rotations to find T.
- Repeat the measurement of T and calculate a mean value for each mass M.
- Keep a constant length for the string for each value of M.
- Plot a graph of against to check if it is a straight line, which would validate the relationship.
Step 3
Comment on this suggestion.
Answer
The use of a video recording could enhance the determination of T by providing a visual reference for when one rotation starts and ends, allowing for more precise timing. However, the effectiveness will depend on the quality of the recording and the clarity of the motion observed. If the video quality is poor, it may not significantly improve the measurements.