Answer:
The length of the beam increasing is 9.64 ft/s.
Explanation:
Given that,
Height = 210 ft
Distance =290 ft
According to figure,
We need to calculate the angle
....(I)
Put the value of x in the equation


Now, 
On differentiate of equation (I)


Put the value in the equation



Hence, The length of the beam increasing is 9.64 ft/s.
A soccer ball takes 20 s to roll 10 m.
Speed of the soccer ball
= 10/20 m/s = 1/2 m/s
Answer:
8 signals received by twin A during the trip.
Explanation:
Given that,
Distance = 12 light year
Speed = 0.6 c
Time = 1 year
We need to calculate the time by A
Using formula of time

Put the value into the formula


Similarly,
The expression for distance cover by A



We need to calculate the time
Using formula of time



We need to calculate the signals received by twin A
Using formula for number of signals

Put the value into the formula


Hence, 8 signals received by twin A during the trip.
b. the forces of attraction among them limit their motion.