5. A 30N stone is dropped from a height of 10.0m and stikes the ground with a ve

Question

5. A 30N stone is dropped from a height of 10.0m and stikes the ground with a velocity of 13.0m/s. What is the energy lost to air friction when it reaches the ground?

6. A 700 Newton Marine in basic training climbs at 10meters wall vertical rope at a constant speed in 8 seconds. What is his power output?

7. A neutron star is a nearly perfect spherical object, it is extremely dense. one under study has rotation of 520revolutions per second. Given a radius of 12km and a mass of 2.2 suns, what is its kinectic energy in joules? (mass of sun is 1.99 x 10^22kg)

Explanation / Answer

Number 5

Energy Lost = mgh - .5mv^2

E = (30)(10) - (.5)(30/9.8)(13)^2

E = 41.3 J

Number 6

P = Fd/t

P = (700)(10)/8

P = 875 Watts

Number 7)

KE = .5Iw^2

I = 2/5(2.2)(1.99 X 10^30)(12000)^2 = 2.52 X 10^38 kg m^2

KE = .5(2.52 X 10^38)(3267)^2

KE = 1.346 X 10^45 J

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