Definitions Flashcards
Define principle of moments
For an object to be in equilibrium the sum of the anticlockwise moments equals the sum of the anticlockwise moments (no turning moment)
When is an object in equilibrium
- Sum of anticlockwise moments = sum of clockwise moments
- All vertical forces cancel and all horizontal forces cancel
Define a couple
A pair of opposite and equal forces separated by distance d, acting about point p, the turning effect at point p is equal to one of Forces multiplied by the perpendicular distance between the forces
Define centre of mass
Where all of an objects mass appears to act about and moments cancel
Define a Newton
Force required to accelerate 1kg by 1ms^-2
Define a joule
Work done by 1N through a distance of 1m in direction of the force
Law of conservation of energy
Energy is never created or destroyed just converted between different types
What is Hooke’s Law?
The extension of a spring is proportional to the force applied to it as long as the limit of proportionality is not exceeded
What is stress
Force per unit area
What is strain
Ratio of extension to original length
What is Young’s Modulus?
Stiffness constant of a material
What is a longitudinal wave?
A propagating wave with oscillations in the same direction as propagation/energy transfer
What is a transverse wave?
A propagating wave with oscillations perpendicular to the direction of propagation/energy transfer
What waves can be polarised?
Transverse waves
Which waves can’t be polarised?
Longitudinal
What is a stationary wave?
Formed when 2 waves of similar frequency travelling in opposite directions interfere and the resultant wave is the vector sum of each waves displacements at that point by the principle of superposition.
What is diffraction?
Spreading out of a wave when passed through a slit, around an obstacle
What are coherent sources
Same frequency and constant phase relationship
What happens when constructive interference occurs?
2 waves intersect and interfere through principle of superposition and the resultant displacement. The vector sum of the 2 waves displacement at that point and the phase difference between the 2 waves is a whole number of wavelengths
What are the differences between single and double spit diffraction?
Single - Wide central maxima 2x width of others and reduction in intensity going away
Double - Same intensity same width going out
Define a moment
Force multiplied by perpendicular distance between force and the pivot
