Physics exam 2
A bug hits the windshield of a car which is moving at 60 mph. Which is true of the
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magnitude of the impact forces? (is the force on the bug bigger, less than, or equal to
the car?) - -They are equal forces
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A weight is whirled around a string in a vertical direction. What is the tension in the
string when the object is at the highest point? - -0 N
A woman normally weighs 125 lb. If she is standing on a spring scale in an elevator
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that is traveling downward, but slowing up, will the scale read more than, less than,
or equal to 125 lbs? - -more than
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Although swinging a weight in a vertical circle is not considered a case of universal
circular motion, how can we still use this case in a ucm problem? - -you can
still treat it as a ucm problem when the wieght is at the top or bottom of the circle
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At which end of a massless rope holding a mass at the end will tension be greatest?
- -Tension is uniform throughout the rope
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At which end of a non-massless rope holding a mass at the end will tension be
greatest? - -It will be greatest at the top of the rope
Between a liquid and gas, which exerts a greater drag force? - ✅✅-the liquid
exerts a bigger drag force
Between gases and liquids, which are more viscous? - ✅✅-liquids
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Can a body be in equilibrium with only 1 force acting on it? why or why not? -
-No because if there's one force, nothing can canel it out in order to get a net
force of zero
How can you use the density of an object to determine its mass? - ✅✅-multiply the
density by the valume of the object
how do you calculate the net force on an object? - ✅✅-take the sum of all forces
acting on it, including their direction and sign
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How do you determine the static friction experienced by an object at rest? -
-you add up all the other force vectors to determine the magnitude of the
component parallel to the surface. The static friction will be equal in magnitude to
this force and opposite in direction
, How do you obtain net force geometrically from a free body diagram? - ✅✅-add
the vectors in the free body diagram
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How does mass of an object incorporate itself into the equation for determining
kinetic friction? - -The mass is directly proportional to the weight of an object,
and the weight corresponds to the normal force on the object, which is involved in
the equation for kinetic friction
How does texture affect kinetic friction? - ✅✅-a rough textured surface
experiences more friction than a smooth surface
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How does the acceleration change if you have a cart on an air track when the air is
off vs on and why? - -The magnitude of acceleration is smaller and will barely
be accelerating at all (when it is decelerating at a larger magnitude without air)
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How does the net force change if you have a cart on an air track when the air is off
vs on and why? - -Net force will still be opposite the direction of travel, but the
magnitude will be smaller in magnitude because there is less frictional force on the
cart
How many newtons are in a pound? - ✅✅-4.45 N
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If a block is sliding along a table and experiences kinetic friction, what other type of
friction exists and what is its effect/. Why does this occur? - -The block also
exerts a friction force on the table, pulling the table in the direction of motion. This
corresponds to Newton's third law, so the two friction forces are equal in magnitude
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If a weight is suspended from the roof of an elevator by a spring with length L, what
happens to the length of the spring as the elevator accelerates - -the length
decreases
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If a weight is suspended from the roof of an elevator by a spring with length L, what
happens to the length of the spring as the elevator accelerates upwards? - -the
length increases
If an apple is sitting on a table and the table is removed, why is the force of the earth
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on the apple and the force of the apple on the earth not an action reaction pair? -
-because the two forces acting on the apple are not a mutual interaction
between objects
If an elevator is moving downward at a constant speed and two blocks are stacked
on top of each other on the floor of the elevator, is the magnitude of the force of the
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bottom block on the top block greater than, less than, or equal to the magnitude of
the force of the earth on the top block? - -equal to
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