Answer:
0.3257 seconds
39.67 m/s
Explanation:
Speed = 263 km/h
Converting to m/s
Distance to travel = 23.8 m
Time = Distance / Speed
The time taken to go from one end of the court to the other is 0.3257 seconds
Time = 0.6 s
Speed = Distance / Time
The speed of the tennis ball is 39.67 m/s
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.