The total momentum before a collision is equal to the total momentum after the collision if no external forces act on the system.
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Answer:
Part a)

Part b)

Explanation:
Part a)
As we know that the period of revolution of the planet is given by

now we know that

T = 6.3 days

now we have


Part b)
As we know that mass of sun is given as

now we have


Answer:
A) first laser
B) 0.08m
C) 0.64m
Explanation:
To find the position of the maximum you use the following formula:

m: order of the maximum
λ: wavelength
D: distance to the screen = 4.80m
d: distance between slits
A) for the first laser you use:

for the second laser:

hence, the first maximum of the first laser is closer to the central maximum.
B) The difference between the first maximum:

hence, the distance between the first maximum is 0.08m
C) you calculate the second maximum of laser 1:

and for the third minimum of laser 2:

Finally, you take the difference:

hence, the distance is 0.64m
He identified triads of elements that had similar properties