1)A rock of mass m is dropped to the ground from a height h. A second rock, with
ID: 1307995 • Letter: 1
Question
1)A rock of mass m is dropped to the ground from a height h. A second rock, with mass 3m, is dropped from the same height. When the second rock strikes the ground, which of the following best describes its kinetic energy?
a) nine times that of the first rock
b) the same as that of the first rock
c) thrice (3x) that of the first rock
d) impossible to determine
e) one-third as much as that of the first rock
2) A 1.0 hp engine compared to a .0 hp engine can do twice the work in
a) the same time
b) one-half the time
c) twice the time
d) none of the preceding
Explanation / Answer
c) thrice (3x) that of the first rock..(as mass is 3 times )(conservation of energy yields KE OF FIRST ROCK AT BOTTOM=mgh)
KE OF 2ND ROCK AT BOTTOM =3mgh
thus it is 3times the KE of 1st rock
B)
b) one-half the time
(as the hp is twice time take will be halved )
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