exam 2 solutions

exam 2 solutions - Multiple Choice Questions Clearly circle...

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Unformatted text preview: Multiple Choice Questions Clearly circle the letter of your choice. You do not need to show your work. No points will be . wen to uestions with two or more choices marked. No artial credit will be iven. I. As a car moves forward on a level road at constant velocity, the net force acting on the tires is: (4 points) (a) greater than the normal force times the coefficient of static friction. (b) equal to the normal force times the coefficient of static friction. (C. the normal force times the coefficient of kinetic friction. zero. 3. A worker pushes a sled with a force of 40 N over a level distance of 6.0 m. If a frictional force 0124 N acts on the sled in a direction opposite to that of the worker, what net work is done on the sled? (4 points) (a) 240] (b)2l6] (0) I44] @961 3. Two masses ml and mg, with m] < 1712, have momenta with equal magnitudes. How do their kinetic energies compare? (4 points) (a) KEI < KE; (b) KEI = KE; @KE; > KEZ (d) More informatiOn is needed. 4. A ball with original momentum +4.0 kg-m/s hits a wall and bounces straight back without losing any kinetic energy. The change in momentum of the ball is: (4 points) (a) 0. (b) «4.0 kg'm/s. (c) 4.0 kg-rn/s. 8.0 kg-mfs. 5. A ceiling fan is turned on and reaches an angular speed of 120 rev/min in 20 s. It is then turned offend coasts to a stop in 40 s. In the one minute of rotation, through how many revolutions did the fan turn? (4 points) (a) 20 (c) o (d) 600 o. A disk starts from rest and has a constant angular acceleration. It takes a time '1' to make its first revolution. in time 2T (starting from rest), the disk will make (4 points) (a) ] revolution (b) 2 revolutions revolutions (d) 8 revolutions ’ between the crate and the floor is 0.50. A horizontal force Fl, acts on the crate 1n the +x direction. (a) Draw the free body diagram showing all the forces that are acting on the crate. (4 points) (b) Will the crate move under the action of Fp= 50.0 N? Justify your answer. (5 points) (c) If you increase the value of PI, to 60.0 N, what is the value of static frictional force? (3 points) (d) What is the value of the coefficient of kinetic friction, if Fp=100 N produces an acceleration ol‘0.50 111/52? Draw the free body diagram for the crate in this case. (5+2 points) in : wng (a) What was the rock‘s gravitational potential energy at pomt A"! (3 points) (b) What is the speed of the rock at point B? (5 points) (0) What is the rock’s total energy at point C? What is its kinetic energy at this point? (3+4 points) (d) Will it ever reach the point D? Ifyour answer is “yes”, what is the speed at point D? If "no", what is the maximum height it can reach? (2 + 2 points) '54 (“M $6 1541 Am 5e“ Wat-(1‘. ,1 A2? fl PS I? (a) Find the speed of the bullet just after it emerges from the first block. (5 points) (b) Find the work Wnc done by non-conservative forces in the collision with the first block. (3 points) (c) Find the speed of the second block just after the bullet collides and embeds itself. (5 points) (d) Find the work W done by non-conservative forces in the collision with the second block. (3 points) (6) 1f the time it takes for the bullet to embed itself in the second block is 2.50x10'5s, find the average force between the bullet and the second block. (3 points) 1':l=0 rli:u 1.: L “n G) FF 2 Vb; + m1 t4; : mvbf + "ML/If , =7 MWM‘ : Ml/Lf+m,|/,f i434 : MI/in ~mlvif M : sex/047x tw— /~w/< £0 >___ Bifox (0‘3 1??? MB 5 (a) How long does it take for the flywheel to come to a complete stop? (5 points) (13) What is the angular acceleration of the flywheel? (4 points) (c) How much time is required for it to complete the first 20 revolutions of the 40 revolutions? (5 points) (d) What is the average tangential speed of a point on the rim of the flywheel during the first 20 revolutions? (5 points) 3/: 7/:an : 0.14‘721 £67: @oret/ : (fax 271 m/ a 3 3") 7T m/ J; W; 1 Al” me/g 9% 3,9. ...
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exam 2 solutions - Multiple Choice Questions Clearly circle...

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