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Unformatted text preview: MC True/False Total 24/ Fall 2004 Last Name
Physics 2750 Exam #2 First Name ID# Points for each question are indicated in parentheses. For full credit show your work for solutions to
questions that require calculations. Explain from where you start to solve the problem and show your
math ﬂowing from it for full credit. If you need more space to finish a question, write BPP (Back of the
Previous Page) at the end of the space provided and then complete your work on the back of the previous page. For multiple choice questions, circle the letter for the answer which you believe to be correct.
In all problems take the gravitational acceleration g = I 0 m/sz. Each multiple choice question is worth 3 points. 1. You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You
can either catch the object or deﬂect the object back towards your friend (such that it moves away from you with the same speed it was originally thrown). What should you do in order to minimize your speed
on the skateboard? @ Catch the ball
b) Deﬂect the ball c) Your ﬁnal speed on the skateboard will be the same regardless whether you catch the ball or
deﬂect the ball 2. A 5 kg body is acted on by a horizontal force as shown in the
graph. What impulse is transmitted to the body by the force? F(N) a) lOkgm/s «A, J}, 5  ..... 
ﬁ 20 kg m/s “a; A?
30 kgm/s OM ﬂ
d) 40 kg m/s 3,, Ma. 11m. e) 50 kgm/s WVme 2 6 3. An iceboat is traveling in a circle on the ice. Halfway around the circle the sail and the steering
mechanism fall off the boat. Which statement is correct? a) The boat will continue traveling in the circle because there is no friction b The boat will continue to travel in the circle because its velocity exerts a force on it
The boat will move off on a line tangent to the circle because there is no force on it (1) The boat will move off tangent to the circle because there is a force on it perpendicular to the boat
directed to the outside of the circle e) The boat will move off to the outside perpendicular to the tangent line since a force directed to the
outside of the circle always acts on the boat 4. Boxes A and B are sliding to the right across a frictionless table.
The hand H is slowing them down. The mass of A is larger than the
mass of B. Rank in order, from largest to smallest, the horizontal forces on A,Band H. _ _ gee a 1:BonH:FHonB‘F‘AonB—FBonA FBonH:FHonB>FAonB=FBonA W (~ka 0) FBonHzFHonB<FAonB=FBonA wt (1) FHonB:FHonA>FAonB Frictionless surface 5. A particle with the potential energy shown in the graph is moving to
the right. It has 1 J of kinetic energy at x = 1 m. Where is the particle’s turning point? ) =1 : +\)=L+%=Lr _
{3:222 E *4 Elww 3:33 K=O om wag :» 70.4,... e) x=7m .‘t' i m) 6. A truck breaks down on the road and receives a push from a small compact car as shown in the ﬁgure.
The small car is pushing the truck to get it to cruising speed. After the driver reaches the constant
cruising speed,
the amount of force with which the car pushes on the
truck is equal to that which the truck pushes back on the
car
b) the amount of force with which the car pushes on the
truck is smaller than that which the truck pushes back on the car 0) the amount of force with which the car pushes on the truck is smaller than that which the truck
pushes back on the car (1) the car’s engine is running so the car pushes against the truck, but the truck’s engine is not
running so the truck cannot push back against the car. e) Neither the car nor the truck exerts any force on the other. The truck is pushed forward simply
because it is in the way of the car. 7. Two cars are traveling around identical circular racetracks. Car A travels at a constant speed of 20 m/s.
Car B starts at rest and speeds up with constant tangential acceleration until its speed is 40 m/s. When car
B has the same (tangential) velocity as car A, it is always true that: a) it is passing car A b it has the same linear (tangential) acceleration as car A @ it has the same radial (centripetal) acceleration as car A
d) it has the same total acceleration as car A
e) it has traveled farther than car A since starting 8. In order to jump off the ﬂoor, the ﬂoor must exert a force on you
a) in the direction of and equal to your weight
b) opposite to and equal to your weight.
c) in the direction of and less than your weight
d) opposite to and less than your weight (65$ opposite to and greater than your weight 9. Write TRUE or FALSE for each one of the following statements:
$0392, a) When a baseball hits a home run, the baseball receives a greater impulse from the bat than the bat
does from the ball
freaky; b) As a tile falls from the roof of a building to the ground its momentum is conserved. c) In order to lift a bucket of concrete you must pull harder on the bucket than it pulls down on you
:Fogw‘c, d) Momentum is conserved whenever mechanical energy is conserved
/ e) A particle is traveling in a vertical circle at constant speed. One can conclude that the net force
\ (“9/ acting on the particle is constant. 10. A 5 kg block is placed on top of a 10 kg block (see ﬁgure below). A horizontal force of 45 N is
applied to the 10 kg block, and the 5 kg block is tied to the wall. The coefﬁcient of kinetic friction
between all surfaces is 0.2. (a) Draw a freebody diagram for each block. (b) Determine the tension in the
string. (c) Find the magnitude of the acceleration of the 10 kg block. gzzwzy 50H =5 1? z: 0.2%50 = l0“. _ ; ’ =o,;b<\50>301\\
m asz \OOdeC «\SDH 7 AW. 11. Three pieces of clay, moving as shown in the ﬁgure, hit simultaneous]
the speed and direction of the resulting blob of clay? a» .5)
“ii = is» t
J”) 0.») \57 4
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7w. wq’ﬁ‘mkﬁt wg—l 2% Vx % . wO _ ‘
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9 ’ W > lifjfwm y and stick together. What are Alf 13. The ball launcher in a pinball machine has a spring that has a force constant of 120 N/m (see ﬁgure
below). The surface on which the ball moves is inclined 10.0° with respect to the horizontal. A) If the
spring is initially compressed 5.00 cm, ﬁnd the launching speed of a 100 g ball when the plunger is
released (ﬁnd the speed of the ball at the moment when it is no longer in contact with the spring). B) Find
the maximum height the ball will reach with respect to the release point (when the plunger was
compressed). Friction and the mass of the plunger are negligible. 0» EA: ED 3:) KM U8” Ugh”: KB'tUFD’t 00$
2 ,2”, 0
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a \AL; 12 M , Big \Al 0 3w Bonus question: (5 points) You and three of your friends are driving on a road covered with snow. After stopping for a hot drink,
when starting the car, the wheels start slipping on the snow and rotating in place so you can not move forward. You have no shovel to clean the snow and no cell phone to call for help. Explain what you and
your friends can do to help yourselves. ...
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 Spring '08
 kozstin
 Physics, Force, Friction, Car

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