Calculate the change in potential energy of a 60 kilogram mass that is lifted a

Question

Calculate the change in potential energy of a 60 kilogram mass that is lifted a distance of 45.0 meter above the surface of the earth.

   a.) 18,240 Joule

   b.) 26,460 Joule

   c.) 74,300 Joule

   d.) 93,620 Joule

A 4.0 Kg mass and an 8.0 Kg mass, both initially at rest, each experience the same horizontal impulse (assume the masses are on frictionless surfaces). Therefore, the final velocities of the two masses can be summarized as follows:

   a.) the final velocity of the 4.0 Kg mass equals 2.0 times the final velocity of the 8.0 Kg mass.

   b.) the final velocity of the 8.0 Kg mass equals 2.0 times the final velocity of the 4.0 Kg mass.

   c.) both masses have the same final velocity.

   d.) none of the above is true.

A 3.0 kg mass accelerates uniformly from rest to a final instantaneous velocity of 32.0 m/s in a time interval 6.0 seconds. Determine the final kinetic energy of the object.

a.)    948 Joule

b.) 4312 Joule

c.) 2130 Joule

d.) 1536 Joule

Explanation / Answer

1.

Result : (b) 26,460 J

Explanation:

At ground, potential energy was zero, hence when it is lifted a distance of 45 meter above the ground, then it's potential energy :

PE = mgh = (60kg)(9.8 m/s2)(45 m)= 26,460 J

2.

Result: (a)

Explanation:

we know that impulse = m× (vf-vi)

vi = 0 for both , and impulse is same.

So , (4kg)vf1 = (8kg)vf2

vf1 = 2vf2

Hence final velocity of 4 kg mass equals two times the final velocity of 8 kg mass

3.

Result: (d)

Explanation:

Kinetic energy can be given as :

KE = (1/2)mv2 = (1/2)(3kg)(32)2 = 1536 J

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