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Bertozzi investigated how the kinetic energy of electrons varies with speed - AQA - A-Level Physics - Question 4 - 2022 - Paper 7
Question 4
Bertozzi investigated how the kinetic energy of electrons varies with speed. Which graph shows the variation of kinetic energy with speed? Tick (✓) one box. A B ... show full transcript
Worked Solution & Example Answer:Bertozzi investigated how the kinetic energy of electrons varies with speed - AQA - A-Level Physics - Question 4 - 2022 - Paper 7
Step 1
Which graph shows the variation of kinetic energy with speed?
Answer
The correct graph is C. This graph shows a gradual increase in kinetic energy with speed, which aligns with the principles of relativistic physics where the kinetic energy approaches an asymptote as speed approaches the speed of light.
Step 2
Calculate the speed of a particle when its kinetic energy is equal to its rest energy.
Answer
The relationship between kinetic energy (KE) and rest energy (E₀) can be given by the equation:
To find the speed, we can use the formula:
At the point where kinetic energy equals the rest energy, we have:
Setting them equal gives:
From this, we can simplify and solve for speed, leading to:
Step 3
Discuss the change in the observed mass of a spring when it is stretched.
Answer
The observed mass of an object is related to its energy as described by the equation:
When a spring is stretched, its potential energy increases, which can lead to an increase in its observed mass. This is sometimes viewed as an increase in the energy of the system, thereby suggesting that the mass associated with the energy contributes to the total mass observed.
Moreover, when an object is stretched, it appears as an increase in observed mass due to the energy added to the system. Treating this change in mass under relativistic terms reveals that the difference in observed mass is negligible as neutral.