Physics Principles and Problems 2009

Chapter 9: Momentum and Its Conservation

Chapter Test Practice

 1 The velocity of a 975-kg car is changed from 12.0 m/s to 27.0 m/s in 15.0 s by an external, constant force. What is the magnitude of the force? Need a Hint? A) 9.75×102 N B) 1.46×104 N C) 9.75×103 N D) 975 kg·m/s 2 Linear momentum is the __________. Need a Hint? A) product of the mass and velocity of a moving object B) quantity of motion used with objects rotating about a fixed axis C) average force and the time interval over which it acts D) angular momentum and torque 3 The quantity of momentum used with objects rotating about a fixed axis is called __________. Need a Hint? A) angular momentum B) torque C) uniform circular motion D) centripetal acceleration 4 A constant force of 4.5 N acts on a 7.2-kg object for 10.0 s. What is the change in the object's velocity? Need a Hint? A) 6.3 m/s B) 3.2 m/s C) 1.2 m/s D) 4.33 m/s 5 The product of the average force and the time interval over which it acts is the __________. Need a Hint? A) impulse B) velocity C) acceleration D) linear momentum 6 Your sister's mass is 43.5 kg, and she is riding her 8.00-kg bicycle. What is the combined momentum of your sister and her bike if they are going 2.40 m/s? Need a Hint? A) 85 kg·m/s2 B) 124 kg·m/s2 C) 104 kg·m/s D) 124 kg·m/s 7 The impulse-momentum theorem states that __________. Need a Hint? A) the impulse on an object is equal to the change in momentum it causes B) the force on a moving object is equal to the magnitude of the impulse C) the impulse on an object is greater than the change in momentum it causes D) the impulse on an object is less than the change in momentum it causes 8 Small rockets are used to make tiny adjustments in the speed of satellites. One such rocket has a thrust of 50.0 N. If it is fired to change the velocity of a 75,000-kg spacecraft by 45 cm/s, how long should it be fired? Need a Hint? A) 18.8 min B) 9.4 min C) 22 min D) 11 min 9 The product of mass and velocity of a moving object is defined as its __________. Need a Hint? A) linear momentum B) impulse C) net force D) normal force 10 A 930-kg car traveling 56 km/h comes to a complete stop in 2.0 s. What is the force exerted on the car during this stop? Need a Hint? A) -7.2×103 N B) 7.2×103 N C) -2.5×104 N D) 2.5×104 N 11 In which position does the diver have the smallest moment of inertia? (6.0K) Need a Hint? A) The first B) The second C) The fourth D) The last 12 If an air bag changes a 6.0×101 kg person's speed from 40.0 m/s to 0.0 m/s, what impulse must act on the person? Need a Hint? A) You cannot solve this problem without knowing the time it takes to stop the person. B) 2400 kg m/s C) 1.5 kg m/s D) 0.67 kg m/s 13 Which of the following is the equation for impulse-momentum? Need a Hint? A) FΔt = mΔv B) p = mv C) F = ma D) g = F/m 14 The velocity of a 975-kg car is changed from 12.0 m/s to 27.0 m/s in 15.0 s by an external, constant force. What is the resulting change in momentum of the car? Need a Hint? A) 1.46×104 kg[dot]m/s B) 9.75×102 kg[dot]m/s C) 2.19×105 kg[dot]m/s D) 7.22×104 kg[dot]m/s 15 In Figure 9-4b, in which position does the diver have the largest moment of inertia? (6.0K) Need a Hint? A) The second B) The third C) The fourth D) The last 16 The impulse is the product of the __________. Need a Hint? A) average force and the time interval over which it acts B) mass and velocity of a moving object C) average force and the distance the object travels D) angular momentum and torque 17 FΔt = mΔv is the equation for __________. Need a Hint? A) impulse-momentum B) linear momentum C) angular momentum D) net force 18 Two freight cars, each with a mass of 2.5×104 kg collide. One was initially moving at 3.7 m/s; the other was at rest. They stick together. What is their final speed? Need a Hint? A) 1.9 m/s B) 3.7 m/s C) 0.54 m/s D) 2.4 m/s 19 Before a collision, a 50.0-kg object is moving at +5.0 m/s. Find the impulse that acted on the object if, after the collision, it moves at +8.0 m/s. Need a Hint? A) -1.5×102 kg·m/s B) -4.5 kg·m/s C) 1.5×102 kg·m/s D) 4.5 kg·m/s 20 A 2.00-kg ball, A, is moving at a speed of 5.00 m/s. It collides with a stationary ball, B, of the same mass. After the collision, A moves off in a direction 30.0° to the left of its original direction. Ball B moves off in a direction 90.0° to the right of ball A's final direction. How fast is ball A moving after the collision? Need a Hint? A) 8.66 m/s B) 2.50 m/s C) 4.33 m/s D) 6.83 m/s 21 Two campers dock a canoe. One camper has a mass of 100.0 kg and moves forward at 3.0 m/s as he leaves the canoe to step onto the dock. With what speed do the canoe and other camper move if their combined mass is 175.0 kg? Need a Hint? A) 8.25 m/s B) 1.7 m/s C) 4.0 m/s D) 5.3 m/s 22 A 2.00-kg ball, A, is moving at a speed of 5.00 m/s. It collides with a stationary ball, B, of the same mass. After the collision, A moves off in a direction 30.0° to the left of its original direction. Ball B moves off in a direction 90.0° to the right of ball A's final direction. How fast is ball B moving after the collision? Need a Hint? A) 2.50 m/s B) 5.00 m/s C) 6.83 m/s D) 8.66 m/s 23 All the forces within a closed system are __________. Need a Hint? A) external forces B) angular forces C) internal forces D) due to gravity 24 Before a collision, a 35-kg object is moving at +10.0 m/s. Find the impulse that acted on the object if, after the collision, it moves at +8.0 m/s. Need a Hint? A) -7.0×102 kg·m/s B) 7.0×101 kg·m/s C) -7.0×101 kg·m/s D) -2.8×102kg·m/s 25 In the figure below, if vC is 1 m/s, vD is 7 m/s, and the mass of each ball is 2 kg, how would the magnitudes of the forces exerted by each ball on the other during the collision compare? (12.0K) Need a Hint? A) The magnitude of the force of C on D would be greater than the magnitude of the force of D on C. B) The magnitude of the force of D on C would be greater than the magnitude of the force of C on D. C) The magnitudes of the forces would be equal. D) They do not exert forces on each other. 26 A 4.75-g bullet is fired with a velocity of 120.0 m/s toward a 20.0-kg stationary solid block resting on a frictionless surface. What is the change in momentum of the bullet if it is embedded in the block? Need a Hint? A) -0.57 kg·m/s B) 1.20×103 kg·m/s C) 5.7 kg·m/s D) -1.20×103 kg·m/s 27 When the net external force on a closed system is zero, it is described as __________. Need a Hint? A) non-accelerating B) an isolated system C) motionless D) a normal system 28 A system that doesn't gain or lose mass is said to be __________. Need a Hint? A) inert B) a closed system C) isolated D) an internal system 29 The law of conservation of momentum states that __________. Need a Hint? A) momentum is neither created nor destroyed B) the momentum of any closed system does not change C) the momentum of any system does not change D) the momentum of any closed system with no net external force does not change 30 In the figure below, 9-6, if mC is 1 kg, mD is100 kg, and the initial velocities of both balls are 5 m/s, how would the magnitudes of the forces exerted by each ball on the other during the collision compare? (12.0K) Need a Hint? A) The magnitude of the force of D on C would be greater than the magnitude of the force of C on D. B) The magnitude of the force of C on D would be greater than the magnitude of the force of D on C. C) The magnitudes of the forces would be equal. D) They do not exert forces on each other.