Definitions

Question 1

Define principle of moments

Answer 1

For an object to be in equilibrium the sum of the anticlockwise moments equals the sum of the anticlockwise moments (no turning moment)

Question 2

When is an object in equilibrium

Answer 2

• Sum of anticlockwise moments = sum of clockwise moments

- All vertical forces cancel and all horizontal forces cancel

Question 3

Define a couple

Answer 3

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

Question 4

Define centre of mass

Answer 4

Where all of an objects mass appears to act about and moments cancel

Question 5

Define a Newton

Answer 5

Force required to accelerate 1kg by 1ms^-2

Question 6

Define a joule

Answer 6

Work done by 1N through a distance of 1m in direction of the force

Question 7

Law of conservation of energy

Answer 7

Energy is never created or destroyed just converted between different types

Question 8

What is Hooke’s Law?

Answer 8

The extension of a spring is proportional to the force applied to it as long as the limit of proportionality is not exceeded

Question 9

What is stress

Answer 9

Force per unit area

Question 10

What is strain

Answer 10

Ratio of extension to original length

Question 11

What is Young’s Modulus?

Answer 11

Stiffness constant of a material

Question 12

What is a longitudinal wave?

Answer 12

A propagating wave with oscillations in the same direction as propagation/energy transfer

Question 13

What is a transverse wave?

Answer 13

A propagating wave with oscillations perpendicular to the direction of propagation/energy transfer

Question 14

What waves can be polarised?

Answer 14

Transverse waves

Question 15

Which waves can’t be polarised?

Answer 15

Longitudinal

Question 16

What is a stationary wave?

Answer 16

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.

Question 17

What is diffraction?

Answer 17

Spreading out of a wave when passed through a slit, around an obstacle

Question 18

What are coherent sources

Answer 18

Same frequency and constant phase relationship

Question 19

What happens when constructive interference occurs?

Answer 19

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

Question 20

What are the differences between single and double spit diffraction?

Answer 20

Single - Wide central maxima 2x width of others and reduction in intensity going away
Double - Same intensity same width going out

Question 21

Define a moment

Answer 21

Force multiplied by perpendicular distance between force and the pivot