Edexcel A Level (IAL) Physics-4.2 Core Practical 9: Investigating Impulse- Study Notes- New Syllabus
Edexcel A Level (IAL) Physics -4.2 Core Practical 9: Investigating Impulse- Study Notes- New syllabus
Edexcel A Level (IAL) Physics -4.2 Core Practical 9: Investigating Impulse- Study Notes -Edexcel A level Physics – per latest Syllabus.
Key Concepts:
- CORE PRACTICAL 9: Investigate the relationship between the force exerted on an object and its change of momentum
CORE PRACTICAL 9: Investigate the Relationship Between Force and Change of Momentum
This core practical investigates how the force acting on an object is related to its change of momentum, providing experimental evidence for Newton’s second law of motion.
Aim
To investigate experimentally how the force exerted on an object is related to its change of momentum.
Apparatus
- Dynamics trolley
- Runway or air track (low friction)
- Force sensor or Newton meter
- Light gates or motion sensor
- Data logger or timer
- Masses
- Card or interrupt flag
Method
- Measure the mass \( m \) of the trolley.
- Attach a force sensor to record the force during a collision or interaction.
- Set up two light gates to measure the initial velocity \( u \) and final velocity \( v \).
- Allow the trolley to move along the track and experience a force (e.g. elastic collision with a spring or buffer).
- Record:
- Average force \( F \)
- Time interval \( \Delta t \)
- Initial and final velocities
- Calculate the change in momentum \( \Delta p \).
- Repeat for different forces by changing the speed or mass.
Data Processing
Calculate change in momentum:
\( \Delta p = m(v – u) \)
Calculate impulse:
\( \text{Impulse} = F\Delta t \)
Compare \( F\Delta t \) with \( \Delta p \).
Graph and Expected Relationship
- Plot change in momentum \( \Delta p \) on the y-axis.
- Plot impulse \( F\Delta t \) on the x-axis.
- Graph should be a straight line through the origin.
Conclusion:
\( \Delta p \propto F\Delta t \)
This confirms Newton’s second law.
Example Results
| Force (N) | Time (s) | Impulse \( F\Delta t \) (N s) | \( \Delta p \) (kg m s⁻¹) |
|---|---|---|---|
| 2.0 | 0.30 | 0.60 | 0.62 |
| 3.0 | 0.30 | 0.90 | 0.88 |
| 4.0 | 0.30 | 1.20 | 1.18 |
Safety Considerations
- Ensure the runway is stable and level.
- Avoid excessive speeds to prevent equipment damage.
- Secure sensors properly.
Sources of Error and Improvements
- Friction: use an air track or smooth runway.
- Timing errors: use electronic light gates.
- Force fluctuations: use data logging to find average force.
- Mass uncertainty: measure mass accurately including attachments.
Conclusion
- The experiment shows that impulse equals change in momentum.
- The relationship \( F\Delta t = \Delta p \) is verified.
- This provides strong experimental support for Newton’s second law of motion.