Question

A 5.0 kg particle and a 2.7 kg particle have a gravitational attraction with a magnitude of 2.2 10-12 N. What is the gravitational potential energy of the two-particle system?

a) A 5.0 kg particle and a 2.7 kg particle have a gravitational attraction with a magnitude of 2.2 10-12 N. What is the gravitational potential energy of the two-particle system?
(I got a) which is -4.451E-11 J)

b) If you triple the separation between the particles, how much work is done by the gravitational force between the particles?

c) How much work is done by you?



Well, the force depends on the inverese of distance squared, the energy is INT f*dx

The integral is constnt/r. The constant is Gm1M2. So, GPE must be Gm2m2/r, but

F=GM1M2/r^2 or r = sqrt GM2M1/F, so put that in, and you have E.

If you triple the distance, F is down to 1/9 of before.

Work done by you is the beginning energy at r and the final energy at 3r

I don't understand what you mean about the work I have done, is it the same as the magnitude as b)? different signs?

If you triple the distance, F is down by 1/9, so you have a new F to put in the formula...

GPE must be Gm2m2/r, but

F=GM1M2/r^2 or r = sqrt GM2M1/F, so put that in, and you have E.


Thank you, I GOT IT!

A diver descends from a salvage ship to the ocean floor at a depth of 35 m below the surface. The density of ocean water is 1.025x10^3 kg/m^3.

a) Calculate the guage pressure on the diver on the ocean floor.

b) Calculate the absolute pressure on the diver on the ocean floor.

The diver finda a rectangular aluminum plate having dimensions
1.0m x 2.0m x 0.03m. A hoisting cable is lowered from the ship and the diver connects it to the plate. The density of aluminum is 2.7x10^3 kg/m^3. Ignore the effects of viscosity.

c) Calculate the tension in the cable if it lifts the plate upward at a slow, constant velocity.

d) Will the tension in the hoisting cable increase, decrease, or remain the same if the plate accelerates upward at 0.05m/s^2? Justify your answer.

Answer 1

a. Pguage=pgh=1.025E3(9.8)(35)=351575n/m2
b. Pabsolute=Po+Pguage=452575
c. gives you density and volume so convert to kg as the mass. T=mg=1587.6 N
d. Increase F=ma, so when it is accelerating there is a greater force pushing down on it