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Name: __________________________ Date: _____________ 1.The work done by gravity during the descent of a projectile is: positive .! 1 kg block is lifted vertically 1 m by a boy. The work done by the boy is about: 1# $ %.! man wishes to pull a crate 1& m across a rough floor by e'erting a force of 1## N. The coefficient of kinetic friction is #.&. (or the man to do the least work) the angle between the force and the hori*ontal should be: # +.!n ideal spring is hung vertically from the ceiling. ,hen a .# kg mass hangs at rest from it the spring is e'tended -.# cm from its rela'ed length. ! downward e'ternal force is now applied to the mass to e'tend the spring an additional 1# cm. ,hile the spring is being e'tended by the force) the work done by the spring is: %.- $ &.The weight of an object on the moon is one si'th of its weight on the /arth. The ratio of the kinetic energy of a body on the /arth moving with speed
V
to that of the same body moving with speed
V
on the moon is: 1:1 -.Two objects with masses)
m
1
and
m
) have the same kinetic energy and are both moving to the right. The same constant force
¢
is applied to the left to both masses. 0f
m
1
+
m
) the ratio of the stopping distance of
m
1
to that of
m
is: 1:1 2.! particle starts from rest at time
t
# and moves along the
x
a'is. 0f the net force on it is proportional to
t
) its kinetic energy is proportional to:
t
+
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4.,hich of the following five units represents a 5uantity that is N6T the same as the other four7 !8joule 98erg 8watt D8foot
⋅
pound /8newton
⋅
meter ;.!n escalator is used to move # people <-# kg each8 per minute from the first floor of a department store to the second floor) & m above. The power re5uired is appro'imately: 1### , 1#.! good e'ample of kinetic energy is provided by: !8a wound up clock spring 98the raised weights of a grandfather=s clock 8a tornado D8a gallon of gasoline /8an automobile storage battery 11.! golf ball is struck by a golf club and falls on a green eight feet above the tee. The potential energy of the /arth ball system is greatest: !8just before the ball is struck 98just after the ball is struck 8just after the ball lands on the green D8when the ball comes to rest on the green /8when the ball reaches the highest point in its flight 1.! . kg block starts from rest on a rough inclined plane that makes an angle of &
°
with the hori*ontal. The coefficient of kinetic friction is #.&. !s the block goes .# m down the plane) the mechanical energy of the /arth block system changes by: ;.4 $
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1%.!n ideal spring is used to fire a 1&.# g block hori*ontally across a frictionless table top. The spring has a spring constant of # N>m and is initially compressed by 2.# cm. The speed of the block as it leaves the spring is: .- m>s 1+.! toy cork gun contains a spring whose spring constant is 1#.# N>m. The spring is compressed &.## cm and then used to propel a -.## g cork. The cork) however) sticks to the spring for 1.## cm beyond its unstretched length before separation occurs. The mu**le velocity of this cork is:.## m>s 1&.! ball of mass
m
) at one end of a string of length
L
) rotates in a vertical circle just fast enough to prevent the string from going slack at the top of the circle. The speed of the ball at the bottom of the circle is:!8 98 %8 +D8 &/8 2
gL gL gL gL gL
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1-.Three identical blocks move either on a hori*ontal surface) up a plane) or down a plane) as shown below. They all start with the same speed and continue to move until brought to rest by friction. ?ank the three situations according to the mechanical energy dissipated by friction) least to greatest.) 1) %12.! machinist starts with three identical s5uare plates but cuts one corner from one of them) two corners from the second) and three corners from the third. ?ank the three plates according to the
x
coordinates of their centers of mass) from smallest to largest.1 and % tie) then 14.The center of mass of a system of particles has a constant velocity if: !8the forces e'erted by the particles on each other sum to *ero 98the e'ternal forces acting on particles of the system sum to *ero 8the velocity of the center of mass is initially *ero D8the particles are distributed symmetrically around the center of mass /8the center of mass is at the geometric center of the system
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