Practice Test #2, Number 1

1. Which of the following is one of the conditions for equelibrium? (a) The net force is a constant (non zero). (b) The net torque is a constant (non-zero). (c) The net lever arm is zero. (d) The net force is zero. (e) The net torque is clockwise.

2. Two children are sitting at the ends of a board which is pivoted at the boards center (a see-saw). The situation is such that the board is balanced and does not move. If the child on the right side of the board leans out (away from the pivot), what will the board do? (a) Rotate such that the child on the right will mnove toward the ground. (b) Rotate such that he child on the right will move away from the ground. (c) Nothing. (d) Explode. (e) Turn Blue.

3. A string is placed through a paperclip, and then the sting is suspended between two walls. Under what condition will the tension in the string be the smallest? (a) Since a paperclip has very little mass, the string can support the paperclip without any tension under any circumstance. (b) If the string is pulled tight (ie, it does not sag very much). (c) If the string is allowed to sag. (d) If the momentum of the paperclip is conserved. (e) If the total energy of the paperclip is conserved.

4. A baseball is caught by a person. While catching the ball, the person may move their hand backwards. What is the effect does moving the hand backwards have on the impulse felt by the catchers hand (as compared to catching the ball without a backward movement of the catching hand)? (a) It depends on the mass of the baseball. (b) It depends upoon the mass of the person's hand. (c) The impulse is increased. (d) The impulse is decreased. (e) There is no effect on the impulse.

5. A steel wire stretches 10 mm wthen a load is hung from it. If a new wire made of the same material but with a cross sectional area twice the first is used to support the same load, the new wire will stretch (a) the same amount. (b) not at all. (c) twice as much. (d) half as much. (e) Not enough information given.

6. One of the forms of energy is work. In class, we treated work for systems in linear motion. The appropriate equation for work for a system in rotation is (a) moment of inertia times angular velocity. (b) moment of inertia time angular distance. (c) Torque times angular distance. (d) Torque times angular velocity. (e) Torque times angular accelration.

7. A solid cylinder, a solid sphere, and a hoop all of the same radius and mass, roll without sliding down an inclined plane. The body which gets to the bottom first will be the (you may need to use tables for this one) (a) cylinder. (b) sphere. (c) hoop. (d) They all reach the bottom at the same time. (e) None of the above.

8. At a given moment, the net angular momentum of a system of two identical particles about a certain point is zero. Therefore, we know that the particles (a) must be at rest. (b) must be moving on the same circle in opposite directions. (c) muswt be moving on straight, perpendicular paths. (d) must have the same linear momentum. (e) None of the above.

9. A rectangular box rests on an inclined surface. The base of the box (that is, the part of the box in contact with the surface), is .5 meters by .5 meters. The height of the box (ie, the dimension perpendicular to the surface) is 3 meters. If the incline is at an angle of 35 degrees with respect to the horizontal, will the box tip over? (a) Yes. (b) No. (c) The box will tip over if the coeficient of static friction is very large. (d) The box will tip over only if the mass of the box is large enough. (e) There is not enough information given to answer this question.

10. An arrow is place on a bow, and the bow is pulled back so that the potential energy of the arrow is 100 J. The arrow is aimed horizontally, and then it is fired. When the arrow leaves the bow, it's kinetic energy will be (a) 50 J, with the other 50 J going into work. (b) 10 J, with the other 10 J going into work. (c) 200 J, to compensate for the -100 J of work done on the arrow. (d) 0 J, since all of the potential energy must go into work done on the arrow. (e) 100 J.

11. Three people go from the bottom of a hill to the top. The first person walks up, the second jogs up, and the third runs up as fast as possible. Which individual will do the most work? (a) The first person. (b) The second person. (c) The third person. (d) They all do the same amount of work. (e) It depends upon the who has the most expensive pair of shoes.

12. Friction is an example of (a) a conservative force. (b) a nonconservative force. (c) a normal force. (d) a motivational force. (e) a tensional force.

13. Which of the following is best described as an application of Pascal's Principle? (a) Water falling over a waterfall. (b) A student studying for a physics exam, which causes their brain to begin to smoke. (c) A hydraulic lift (you exert a force on one side, and a larger force is produced on the other). (d) A can of tomatoes. (e) A ship sailing on Lake Erie.

14. The hydraulic automobile jack illustrates (a) Archimede's principle. (b) Pascal's principle. (c) Hooke's law. (d) Newton's third law. (e) Newton's second law.

15. Three containers are filled with water. The first container is cylinderical, and has a radius of 10 m. The second container is also cylinderical, but the radius is only 1 cm. The third container is shaped like a pyramid (with an open top) so that is has a wide, square bottom, each side of which is 1 m. Each container is filled to exactly the same height with water. Which container will have the highest pressure at the bottom. All containers are open to the air at the top. (a) The first container. (b) The second container. (c) The third container. (d) All pressures are the same at the bottom. (e) There is not enough information given to answer this question.

16. An object at rest achieves an angular speed of 10 rev/sec is 1 sec. Through what angle has the object roatated in this time? (a) 0 pi. (b) 5 pi . (c) 10 pi. (d) 15 pi. (e) 20 pi.

17. If a 20 kW engine can raise a load 50 m is 10 sec, how long will it take to raise the same load 100 m? (a) 5 sec. (b) 10 sec. (c) 20 sec. (d) 40 sec. (e) 80 sec.

18. A block slides from rest down a frictionless incline reaching the bottom at 4 m/sec. On the next run, the block gets a push and starts down at 3 m/sec. At what speed does the block arrive at the bottom (in m/sec)? (a) 7. (b) 5. (c) 3. (d) 1. (e) None of the above.

19 . A rocket of mass 1000 kg has a load of fuel (mass of the fuel = 50 kg). The mass of the fuel is not included in the 1000 kg rocket mass. The fuel is ejected form the back of the rocket at 100 m/sec. As a result, the rocket will move with a speed (in m/sec) (a) 1.0. (b) 2.0. (c) 3.0. (d) 4.0. (e) 5.0.

20. Two billiard balls of equal mass are moving with equal but opposite velocities of magnitude 5 m/sec and they collide head on into a peice of bubble gum to which they both stick. What will their mutual speed be after the collision? (a) 0 m/sec. (b) 5 m/sec. (c) 10 m/sec. (d) 20 m/sec. (e) 30 m/sec.

21. Two small rockets are mounted tangentially on diametrically opposite sides of a cylindrical shaped artificial satellite. The spacecraft has a 1.0 m diameter and a mass of 400 Kg. The rockets each develop a thrust of 5.0 N, are oppositiely directed, and are aligned to produce a maximum spin-up of the craft. (a) How much torque is produced on the satellite as a result of firing both thrusters? (b) What is the resulting angular acceleration when both rockets are fired? (c) The thrusters fire for 100 sec, after which they are shut off. What is the angular speed of the satellite after the thrusters are shut off? (d) After the thrusters are shut off, an antenna is erected from the satellite which doubles the satellites moment of inertia. What is the angular speed of the satellite after the antenna is erected?

22. A rollercoaster (of mass 100 kg) travels along the rails making the track. The coaster starts at point A (the highest point) at a height of 20 m above the ground. It goes down the hill to point B (ground level) up another hill to C (at a height of 15 m above the ground. If goes back down that hill to ground level at D, and runs along a horizontal section, satopping at point E. Assume that the coaster begins at A from rest. When the coaster reaches D, the section from D to E has friction, and the coaster comes to rest at E. Assume that the rails are all frictionless except from D to E, and the g = 10 m/sec2. (a) What is the speed of the coaster at B? (b) What is the speed of the coaster at C? (c) If the coaster comes to rest at E, how much work was done by friction from D to E?

Answer Key: 1 .D 2. A 3. C 4. E 5. D 6. C 7. B 8. E 9. E 10. E 11. D 12. B 13. C 14. B 15. D 16. C 17. C 18. B 19. E 20. A

Practice Test 2, Nuber 2

1. Which of the following conditions is required in order for an object to be stable? (a) The object must be shaped like a pyramid. (b) The center of mass of the object must be relatively high. (c) The center of mass ofhte object must be relatively low. (d) The center of mass of the object must be located above the base the support. (e) The center of mass of the object must be located outside of the base of support.

2. A rope is suspended between two trees and a package is tied to the middle of the rope. In which of the following cases will the tension in the rope be the largest? (a) The rope sags a great deal. (b) The rope sags only a small amount. (c) The rope is tied to locations high on the tree. (d) The rope is tied to locations low on the tree. (e) None of the above.

3. Two identical thin rods of length L and mass M are arranged in the following way. The first rod is placed along the x axis, with one end at x = L/2 and the other at x = 3L/2. The second rod is parallel to the first, but at a distance y = L from the first. The second rod also has one end at x = L/2 and the other end at x = 3L/2. What is coordinates of the center of mass? You may need to sketch this. (a) x = L/2, y = L. (b) x = L, y = L/2. (c) x = L/2, y = L/2. (d) x = 3L/2, y = L. (e) x = 0, y = 0.

4. When a car with a convertable top drives down the road, the top will bulge out. The effect is most closely related to which of the following? (a) Pascal's principle. (b) Archimedes' principle. (c) The principle of continuity. (d) Bernoulli's principle. (e) Prandtl's principle.

5. An object moves in a circle at constant speed. The work done by centripetal force is zero because (a) the displacement for each revolution is zero. (b) the average force for each revolution is zero. (c) the is no friction. (d) the magnitude of the acceleration is zero. (e) the centripetal force is perpendicular to the velocity.

6. A space shuttle moves with a velocity in the +x direction. When it reaches the origin it releases a satellite. Assume that the mass of the sateelite is very small compared to the mass of the shuttle. The satellite has a velocity with components in the +x and -y directions. After the satellite is released, the velocity of the shuttle will have components (a) in the +x and +y directions. (b) in the +x and -y directions. (c) in the -x and +y directions. (d) in the +x direction only. (e) in the +y direction only.

7. A basketball player spins a basketball and ballances it on his finger. It the ball is spinning, it is easier to ballance, in accordance with the statement of (a) the first law for rotation. (b) the second law for rotation. (c) the third law for rotation. (d) conservation of energy. (e) conservation of projetile motion.

8. An iceskater begins her spin with her arms out and then brings them in close to her body. Her spin rate increases. What principle does this illustrate best? (a) an external force changing her rate of spin. (b) an external torque changing her rate os spin. (c) conservation of linear momentum. (d) conservation of angular momentum. (e) conservation of figure skater.

9. The manufacturer of a wire wheel (spokes of negligible mass) want to increase the wheel's radius without increasing the wheel's moment of inertia. If they double the radius, by what factor will they have to reduce the wheel's mass? (a) 2. (b) 4. (c) 6. (d) 9. (e) 16.

10. If a certain job is done slowly, and an identical job is done quickly, both jobs can require the same amount of work but different amounts of (a) energy. (b) power. (c) heat. (d) All of the above. (e) None of the above.

11. Two bodies, A and B, have equal kinetic energies. The mass of A is nine times that of B. The ratio of the momentum of B to that of A is (a) 1/9. (b) 1/3. (c) 1/1. (d) 3/1. (e) 9/1.

12. When an earthquake occurs underground, the first pulse to reach the surface causes the earth to move perpendicular to the surface of the earth (up). The stress in the buildings on the surface will be proportional to the strain, with the constant of proportionality being (a) Young's modulus. (b) Shear modulus. (c) Bulk modulus. (d) Erdei's modulus. (e) Physics modulus.

13. When an earthquake occurs underground, the second pulse to reach the surface causes the earth to move parallel to the surface of the earth (sideways). The stress in the buildings on the surface will be proportional to the strain, with the constant of proportionality being (a) Young's modulus. (b) Shear modulus. (c) Bulk modulus. (d) Erdei's modulus. (e) Physics modulus.

14. According to the equation of continuity, when a fluid flows from a pipe of large cross sectional area to one of smaller cross-sectional area, the speed will (assume the flow is horizontal) (a) increase. (b) decrease. (c) remain unchanged. (d) approach infinity. (e) immediatly drop to zero.

15. According to Bernoulli's equation, when a fluid flows from a pipe of large cross-sectional area to one of smaller cross-sectional area, the pressure will (assume the flow is horizontal) (a) increase. (b) decrease. (c) remain unchanged. (d) appraoch infinity. (e) immediately drop to zero.

16. A block of mass m1 moves at a speed v1 and collides with a stationary object of mass m2.. When they collide they stick together (inelastic collison) and move with a speed V. Which of the following is correct? (a) V^2 = (m1/(m1+m2))v1^2. (b) V = v1 (c) m2V = m1 v1. (d) V = (m1/(m1+m2)) v1. (e) None of the above.

17. A block is slid across a frictionless, level table top. It strikes a horizontal spring, and as a result, the spring is compressed .02 m before the block comes to rest. The spring constant is 10 N/m. What was the kinetic energy (in Joules) of the block before it collided with the spring? Assume no losses due to heat. (a) 0.001. (b) 0.002. (c) 0.02. (d) 0.1. (e) 0.2.

18 A truck of mass 1000 kg is traveling at 20 m/sec when it collides with a fly. The impact lasts for 0.1 sec, and the resulting force on the fly is 200 N. What is the change in momentum of the truck (in Kg-m/sec) as a result of this collision? (a) 0.0 (b) 5.0. (c) 10.0. (d) 20.0. (e) Not enough information given.

19. Water flows through a cylindrical pipe of varying cross-section. The velocity is 3 ft/sec at a point where the pipe diameter is 1 in. At a point where the pipe diamete is 3 in, the velocity is (a) 9 ft/sec. (b) 3 ft/sec. (c) 1 ft/sec. (d) 0.33 ft/sec. (e) 0.11 ft/sec.

20. A rock, which weighs 300 N in air, weighs 200 N when submerged in a fluid of density 5 kg/m3. The volume (in m3) of the rock is (assume g = 10.0 m/sec2) (a) 2. (b) 300. (c) 5.0. (d) 50. (e) 200.

21. You are involved in a head-on collision with another car. When the police arrive, The other person states that you were speeding, and that they would have been able to get out of the way if you had been going the speed limit. You claim that in fact you were not speeding. In order to propoerly understand what happened, the police hire A REALLY SMART PERSON who records the following information as taken from measurements on the car and on the skid marks on the pavement: (a) Both cars are identical (ie, same mass). (b) The skid marks show that after the collision, your car bounced in the -x direction with a speed of 3 m/sec. (c) The skid marks show that after the collision, the other persons car bounced in the +x direction with a speed of 4 m/sec. (d) The speed limit is 3.5 m/sec. Were you speeding? Because the cars bounce off of one another, you can consider the collision to be elastic. PROVE YOUR ANSWER.

22. An uniform steel beam of length 10.0 m and a mass of 200 kg is used to hoist heavy loads at a shipping yard. The beam has 600 kg load suspended from its right end. The beam makes an angle of 30o with respect to a supporting tower, and a cable is used to help in supporting the system. The cable is also conneted to the right end of the beam and the other end of the cable is connected to the tower. The cable is perpendicular to the tower (the tower is vertical and the cable is horizontal). You may need to sketch this figure to get the problem straight. (a) What is the tension in the cable? (b) What are the horizontal and vertical components of the force the hinge exerts on the beam?

Answer Key: 1. D 2. B 3. B 4. D 5. E 6. A 7. A 8. D 9. B 10. B 11.B 12. A 13. B 14. A 15. B 16. D 17. B 18. D 19. D 20. A