5.2 TIDE GENERATION

Question 1

What is the universal law of gravitational attraction?

Answer 1

the force of gravitational attraction of 2 particles of mass M1 and M2 separated by distance r is given by…

F = GM1M2/r^2

where G is the universal gravitational constant 6.67 x 10^-11 Nm^2/kg^2

Question 2

How are tides generated?

Answer 2

• the earth and moon form a single system, mutually revolving around a common centre of mass called the barycentre, with a period of 27.3 days.
• at this point, the gravitational attraction between the earth and moon exactly balances the force required to maintain the moon’s orbit.
• elsewhere, the two forces aren’t in balance and give rise to the so called tide generating force.
• this is not the local vertical variation in the tide generating force that causes water on earth’s surface to be drawn into 2 bulges on opposite sides of earth.
• instead, it’s the small horizontal tractive force; the component of the force tangential to earth’s surface which causes the accelerations needed to move water.

Question 3

How much weaker are solar forces than lunar forces?

Answer 3

Solar forces are a factor of 0.46 weaker than lunar forces; much greater mass is offset by its greater distance from earth.

Be able to do equation using 2mpg(m1/me)(a/r)^3