Dynamics and Relativity 2

Question 1

work

Answer 1

F.s=|F||s|cos theta

i.e work is a scalar

Question 2

work total

Answer 2

sum of all segments

w= ∫F.ds

Question 3

Hooke’s Law

Answer 3

Fx=-kx

-ve shows F direction opposite to extension direction

Question 4

power

Answer 4

dw/dt

w= ∫T/0 P dt

Question 5

if power constant

Answer 5

P=wt

Question 6

P=dw/dt=..

Answer 6

d/dt(F.s)=F.v

Question 7

conservation of energy W=Fs=…

Answer 7

mg(y-y0)

U=mgy

Question 8

work done is stored as

Answer 8

potential energy

ΔU+Δk=0

Question 9

since ΔU=mg(y-y0), ΔK=

Answer 9

-mg(y-y0)

Question 10

elastic potential energy

Answer 10

U=1/2kx^2

Question 11

Wspring=

Answer 11

U1-U2

Question 12

work done is…

Answer 12

independent of path taken

Question 13

to get gravitational potential,

Answer 13

integrate force

Question 14

force is rate of change of

Answer 14

momentum

Question 15

impulse

Answer 15

J=FΔt (units Ns)

Question 16

conservation of linear momentum

Answer 16

total momentum before a collision is equal to the total momentum after a collision in the absence of external forces

Question 17

elastic collision

Answer 17

total mechanical energy conserved

Question 18

inelastic collision

Answer 18

total mechanical energy not conserved

Question 19

angular momentum cross products

Answer 19

L=rxp=rxmv (r is position vector ie origin to particle)

Question 20

|rxp| =

Answer 20

rpsintheta

Question 21

angular momentum is perpendicular to

Answer 21

both r and p

Question 22

torque cross product

Answer 22

t=rxF

Question 23

torque

Answer 23

rate of change of angular momentum

Question 24

if fixed radius,

Answer 24

v=wr so k=1/2mw^2r^2

Question 25

moment of intertia

Answer 25

sum of mr^2

k=1/2Iw^2

Question 26

special relativity postulates

Answer 26

1.laws of physics same in all reference frames
2. c constant

Question 27

inertial

Answer 27

not accelerating

Question 28

c constant proved by

Answer 28

Michelson-Morely experiment, no interference between light rays so same speed

Question 29

length contraction only occurs

Answer 29

along direction of motion

Question 30

relativistic momentum

Answer 30

use relativistic mass

p=gamma mv

Question 31

relativistic energy

Answer 31

E=mrelc^2

E=gamma mc^2

Question 32

how photons have energy without mass

Answer 32

combining relativistic momentum and energy gives

E^2=m^2c^4+p^2c^2