Option Flashcards
What is meant by the Moment of Inertia of an object?
A measure of the opposition of a body to having its angular velocity changed by an applied torque
What factors affect the moment of inertia of an object?
- The mass of the object
- How the mass is distributed
- The axis that it will be rotated about
Use of Flywheels as a Rotational Kinetic Energy Store
- Large fly wheels can be used to stabilise the energy supply to a system
State the Law of conservation of angular momentum
- The total angular momentum of a system remains constant provided no external torque acts on the system
State 3 uses of a Flywheel
- To smooth out fluctuations in rotational speed
- To store rotational kinetic energy
- To smooth fluctuations in torque/power
Types of Systematic Errors
Parallax Error
- reading a scale at the wrong angle
Zero Error
- when an instrument is badly calibrated
Environmental Factors
- temperature in a room changed and affects your readings
Different kinds of Errors
- Systematic Errors
- caused by a fault with the method or the apparatus
- they effect every reading
- they usually can be identified and removed
- Random errors
- random fluctuations which cannot be avoided
How to reduce uncertainty
- using higher resolution measuring equipment e.g. digital rather than analog, greater no. of significance
- helps avoid systematic errors
- minimises the effect of random errors - take repeat readings if possible
- more reliable mean value
- allows for you to identify anomalous readings
- helps better estimate uncertainty of readings
How do you improve accuracy?
- accuracy is how close to the true value you are when measuring
- to improve accuracy you must be calibrating measuring instruments
- if uncalibrated will lead to systematic errors in all readings
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What is the resolution?
- the smallest scale division
What is precision?
- How reproducible your measurements are
- A set of measurements that are close together show high precision
What limits rotational kinetic energy?
- the structural integrity of the object
How do fly wheels smooth torque and speed
- power is not produced continuously but only in the form of ‘power strokes’
- as a result the power systems/ engines produce a torque that fluctuates
- uneven torque causes jerky motions in vehicles ( a waste of energy)
- adding a fly wheel which speeds up or slows down over a period of time due to its intertial will take that KE as rotational KE
- this smooths out the fluctuations in torque
- to increase power and torque combustion engines have multiple combustion cylinders
KERS (kinetic energy recovery systems)
- ## regenerative breaking
