Answer:
The time is 5.10 sec.
Explanation:
Given that,
Component of velocity are 30 m/s and 40 m/s.
We need to calculate the resultant velocity
Using formula of resultant velocity
Put the value into the formula
[
We need to calculate the time
Using equation of motion
Put the value into the formula
Hence, The time is 5.10 sec.
Answer:
The farther star will appear 4 times fainter than the star that is near to the observer.
Explanation:
Since it is given that the luminosity of the 2 stars is same thus they radiate the same energy per unit time
Consider a spherical wave front of energy 'E' that leaves both the stars (Both radiate 'E' as they have same luminosity)
This Energy is spread over the whole surface area of sphere Thus when the wave front is at a distance 'r' the energy per unit surface area is given by
For the star that is twice away from the earth the distance is '2r' thus we will receive an energy given by
Hence we sense it as 4 times fainter than the nearer star.