1. At the surface of a certain planet, the gravitational acceleration g has a ma

Question

1. At the surface of a certain planet, the gravitational acceleration g has a magnitude of 11.5 m/s2. A 2.2 kg brass ball is transported to this planet.
(a) What is the mass of the brass ball on the Earth and on the planet?
_____ Earth
_____ Planet

(b) What is the weight of the brass ball on the Earth and on the planet?
___ Earth
___ Planet

2. A 399 kg piano slides 3.7 m down a(n) 27° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (see figure). The effective coefficient of kinetic friction is 0.40.

(a) Calculate the force exerted by the man.
___ N

(b) Calculate the work done by the man on the piano.
___ J

(c) Calculate the work done by the friction force.
___J

(d) Calculate the work done by the force of gravity.
___ J

(e) Calculate the net work done on the piano.
___ J

Explanation / Answer

(1) Mass : (a) 2.2 Kg Earth    2.2 Kg    Planet Weight : (b) 2.2*9.8 = 21.56 N Earth            2.2*11.5 = 25.3 N Planet (2) (a) F = mg( sin - cos)    = 399*9.8(sin27 - 0.4 cos27)    = 3910.2[0.4539 -0.3564]    = 381.24 N (b) W1 = - F S = - 381.24 * 3.7                    = - 1410.6 J (c) W2 = - mg cos S        = - 0.4*399*9.8*cos27*3.7        = - 5156.34 J (d) W3 = mg sin S        = 399*9.8*sin27*3.7        = 6568.216 J (e) W = W1 + W2 + W3     = - 1410.6 - 5156.34 + 6568.216     = 1.276 J      

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