Table of contents
Circular Motion
Define radian [2]
w17 42 Q3 [2]
- Angle subtended at the centre of circle
- … by an arc equal in length to the radius of the circle.
What is meant by angular velocity [2]
For all contexts: [1]
- Angular displacement swept out by radius, per unit time
For some contexts, additional [1]
What is meant by angular frequency [1]
m17 42 Q3 [1]
- angular frequency = 2π × frequency
What is meant by displacement [1]
w19 43 Q4 [1]
- Distance from a point in a given direction.
Gravitation
Define gravitational potential at a point [2]
- Work down in bringing unit mass
- … from infinity to the point
What is meant by a gravitational field [2]
- Region of space area
- … where a mass experiences a force
What is meant by a line of gravitational force [1]
s18 42 Q1 [1]
- Tangent to the line gives direction of force on a mass
What is meant by gravitational force [1]
s20 43 Q1 [1]
- Force acting between two masses.
Why the gravitational field strength close to the Earth’s surface is approximately constant [3]
s18 42 Q1
- At surface, lines of force are radial.
- Earth has large radius so lines are approximately parallel
- … so constant field strength.
Why gravitational potential near a mass is always negative [3]
m19 42 Q1
- Gravitational force is always attractive.
- Potential at infinity is zero.
- Potential energy decreases as mass approaches.
State Newton's law of gravitation [2]
w17 42 Q1 [2]
- Force between two point masses
- … is proportional to product of masses and inversely proportional to square of separation
Oscillations
Why peak frequency f0 in a-f graphs [2]
f0 is at natual frequency of system.- This is at driver frequency.
Define Simple Harmonic Motion [2]
- Acceleration proportional to displacement
- … and directed towards a fixed point.
Define oscillations [1]
- Backward and forward motion between two limits.
Define free oscillations [1]
- Oscillations without external forces.
What is meant by damping [2]
- Continuous loss of energy
- …, caused by force acting in opposite direction to the motion.
Damping for oscillating Magnet with coils [5]
The magnet oscillates and interacts with a coil, causing magnetic induction hence damping.
- Oscillations are damped.
- Coil cuts magnetic flux as (magnet/coil) moves
- …, current induced in the coil
- …, current dissipates energy
- …, so the energy of the system loss.
- Force opposes motion of magnet
What is meant by natural frequency [1]
m18 42 Q4
- Frequency at which body will vibrate when there is no resultant external resistive force acting on it.
What is meant by resonance [2]
- large amplitude of vibration
- … when impressed frequency equal natural frequency of vibration.
Benefits and drawbacks of resonance [2]
Benefits [1]
Drawbacks [1]