Answer:
The speed of the plank relative to the ice is:

Explanation:
Here we can use momentum conservation. Do not forget it is relative to the ice.
(1)
Where:
- m(g) is the mass of the girl
- m(p) is the mass of the plank
- v(g) is the speed of the girl
- v(p) is the speed of the plank
Now, as we have relative velocities, we have:
(2)
v(g/b) is the speed of the girl relative to the plank
Solving the system of equations (1) and (2)



I hope it helps you!
Answer:
took longer to complete one oscillation, that means its PERIOD increased, and the distance between the peaks of the graph would be longer.
line would be less. the period of oscillation would have any effect on the graph
Explanation:
Given that,
Wavelength of the light, 
Work function of sodium, 
The kinetic energy of the ejected electron in terms of work function is given by :

The formula of kinetic energy is given by :

Hence, this is the required solution.
Answer:
Minimum thickness; t = 9.75 x 10^(-8) m
Explanation:
We are given;
Wavelength of light;λ = 585 nm = 585 x 10^(-9)m
Refractive index of benzene;n = 1.5
Now, let's calculate the wavelength of the film;
Wavelength of film;λ_film = Wavelength of light/Refractive index of benzene
Thus; λ_film = 585 x 10^(-9)/1.5
λ_film = 39 x 10^(-8) m
Now, to find the thickness, we'll use the formula;
2t = ½m(λ_film)
Where;
t is the thickness of the film
m is an integer which we will take as 1
Thus;
2t = ½ x 1 x 39 x 10^(-8)
2t = 19.5 x 10^(-8)
Divide both sides by 2 to give;
t = 9.75 x 10^(-8) m
You could be lying completley still on your bed, and all though it seems you are at rest, you are moving along with the earth around the sun and hence are motion. This is why 'being at rest' is more of a relative term. Hope this helps!