Unformatted text preview: he gravitational force. b) The magnitude of the work done by the gravitational force is larger than that done by the tension force. c) The net work done by the two forces is zero joules. d) The work done by the tension force is zero joules. e) The work done by the gravitational force is zero joules. 2 6. (2 points) A force on a particle is conservative if: a) its work equals the change in the kinetic energy of the particle b) it obeys Newton's second law c) it obeys Newton's third law d) its work depends on the end points of every motion, not on the path between e) it is not a frictional force 7. (2 points) As a particle moves along the x axis it is acted upon by a conservative force. The potential energy is shown below as a function of the coordinate x of the particle. Rank the labeled regions according to the magnitude of the force, least to greatest. a) AB, BC, CD b) AB, CD, BC c) BC, CD, AB d) BC, AB, CD e) CD, BC, AB 8. (4 points) A spring with an elastic constant k = 200 N/m, is initially stretched 3 cm. Calculate the work done in stretching the spring an additional 3 cm. 3 9. A 0.01 kg bullet moving 1000 m/s strikes and gets embedded in a 0.2 kg block initially at rest, as shown. a) With what speed does the block + bullet system start moving upward? (5 points) b) To what maximum height will the block + bullet rise above its initial position? (5 points) 4 10. A 10.0‐kg crate slides along a smooth horizontal frictionless surface at a constant speed of 4.0 m/s. The crate then slides down a frictionless incline (from A to B) and across a second rough horizontal surface (B to C) as shown in the figure. a) What is the kinetic energy of the crate as it slides on the upper surface? (2 points) b) What is the gravitational potential energy of the crate as it slides on the upper surface with respect to the lower surface? (2 points) c) Calculate the total energy of the crate just before starting to slide down the incline (point A). (1 points) d) What is the speed of the crate when it arrives at the lower surface (point B)? (5 points) e) Calculate the work done by the force of gravity on the incline (from A to B). (3 points) 5 f) Consider that the coefficient of friction for the lower rough horizontal surface is = 0.4. How far does the crate slide (from point B) until coming to a stop? (7 points) P1‐8 16/ P9 4/ P10
10/ P11
20/ Total
50/ 6 Physics 2750 Formula Sheet Exam 2 Newton's Second Law Work F F net ma Ffk k N kinetic friction
Fe kx elastic force
aR v2
radial acceleration
R Scalar product A B AB cos Energy
1
K mv 2 kinetic
2
U g mgy gravitational potential W F d Fd cos constant force x f
W F d x Fx dx variable force
xi Average power
W
Pavg t
Instantaneous power dW P F v (when F constant)
dt Ue 12
kx elastic potential
2 Work and Energy
Wnet K
Wmg U g
Wel U e angle between A and B
Energy and Force
dU
Fx dx Linear Momentum p mv Work Kinetic Energy Theorem Newton's 2nd Law d p
Fnet dt W W net K K f K i Conservation of Energy Theorem
Emechanic K U constant
Ei E f
E f Ei Wnon cons Impulse J Favg t p t2 J F dt
t1 Conservation of Momentum Theorem pi p f Center of Mass m r m2 r2 m3 r3 ... rCM 1 1
m1 m2 m3 ... m v m2 v2 m3 v3 ...
vCM 1 1
m1 m2 m3 ... M rCM rdm M vCM ptotal Fnet maCM...
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 Spring '08
 FORGAS
 Physics, Force, Kinetic Energy, Work

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