Answer:
3 hours
Explanation:
180 divided by 60 (mph means miles per hours by the way)
Answer:
Part a)

Part B)
percentage increase is
%
Explanation:
Part a)
As we know that the beat frequency is

after increasing the tension the beat frequency is decreased and hence the tension in string B will increase
So we have


Part B)
percentage increase in the tension of the string will be given as


now we have

so we have


so we have

percentage increase is

The gravitational forces between the Earth and Moon are greatest when the two bodies are closest together. That happens every 27.32 days, when the Moon is at the perigee of its orbit.
Even if this happened at the same time in every orbit, the date would change, because there are not 27.32 days in a month.
But it doesn't happen at the same time in every orbit ... the Moon's perigee precesses around its orbit, on account of the gravitational forces toward the Earth, the Sun, Venus, Mars, and the other planets.