Halliday/Resnick/Walker Fundamentals of Physics 8th edition Classroom Response System Questions Chapter 6 Force and Motion II Reading Quiz Questions

6.2.1. Which one of the following statements concerning the static and kinetic frictional forces is correct? a) When an object is stationary, both static and kinetic frictional forces are acting on it. b) When an object is stationary, only the kinetic frictional force acts on it. c) When an object is sliding, only the static frictional force acts on it. d) The static frictional force acts on an object when it is stationary and the kinetic frictional force acts on it when it is sliding. e) Static and kinetic frictional forces act in the same direction as the normal force.

6.2.1. Which one of the following statements concerning the static and kinetic frictional forces is correct? a) When an object is stationary, both static and kinetic frictional forces are acting on it. b) When an object is stationary, only the kinetic frictional force acts on it. c) When an object is sliding, only the static frictional force acts on it. d) The static frictional force acts on an object when it is stationary and the kinetic frictional force acts on it when it is sliding. e) Static and kinetic frictional forces act in the same direction as the normal force.

6.2.2. Which of the following is not one of the properties of the friction force? a) There is no upper limit to the magnitude of a static friction force. b) The friction force on a moving object is smaller than the friction force on a stationary object. c) If an object is at rest while a force is applied to the object parallel to the surface on which it’s resting, then the friction force on the object is equal in magnitude to the applied force, but oppositely directed. d) The friction force on an object depends on the normal force acting on it. e) If an object is sliding along a surface, the friction force acts in the direction opposite to the object’s velocity.

6.2.2. Which of the following is not one of the properties of the friction force? a) There is no upper limit to the magnitude of a static friction force. b) The friction force on a moving object is smaller than the friction force on a stationary object. c) If an object is at rest while a force is applied to the object parallel to the surface on which it’s resting, then the friction force on the object is equal in magnitude to the applied force, but oppositely directed. d) The friction force on an object depends on the normal force acting on it. e) If an object is sliding along a surface, the friction force acts in the direction opposite to the object’s velocity.

6.2.3. What is the underlying physical reason for the difference between the static and kinetic coefficients of friction of ordinary surfaces? a) The static friction coefficient is due to the presence of cold welds. b) There are fewer cold welds in the case of sliding. c) In the static case, nearly 100 % of the surfaces are in contact at the atomic level. d) When the two surfaces are stationary relative to each other, there are fewer cold welds.

6.2.3. What is the underlying physical reason for the difference between the static and kinetic coefficients of friction of ordinary surfaces? a) The static friction coefficient is due to the presence of cold welds. b) There are fewer cold welds in the case of sliding. c) In the static case, nearly 100 % of the surfaces are in contact at the atomic level. d) When the two surfaces are stationary relative to each other, there are fewer cold welds.

6.3.1. Two identical blocks are pulled along a rough surface as suggested in the figure. Which one of the following statements is false? a) The coefficient of kinetic friction is the same in each case. b) A force of the same magnitude is needed to keep each block moving. c) The normal force exerted on the blocks by the surface is the same for both blocks. d) The magnitude of the force of kinetic friction is greater for the block on the right. e) A force of the same magnitude was required to start each block moving.

6.3.1. Two identical blocks are pulled along a rough surface as suggested in the figure. Which one of the following statements is false? a) The coefficient of kinetic friction is the same in each case. b) A force of the same magnitude is needed to keep each block moving. c) The normal force exerted on the blocks by the surface is the same for both blocks. d) The magnitude of the force of kinetic friction is greater for the block on the right. e) A force of the same magnitude was required to start each block moving.

6.3.2. A block is pulled at constant speed along a rough level surface by a rope that makes an angle  with respect to the horizontal. The applied force along the rope is . The force of kinetic friction between the block and the surface is . Which one of the following actions will increase the frictional force on the block? a) increasing the angle made by the rope b) decreasing the speed of the block c) decreasing the contact surface area d) increasing the contact surface area e) increasing the weight of the block

6.3.2. A block is pulled at constant speed along a rough level surface by a rope that makes an angle  with respect to the horizontal. The applied force along the rope is . The force of kinetic friction between the block and the surface is . Which one of the following actions will increase the frictional force on the block? a) increasing the angle made by the rope b) decreasing the speed of the block c) decreasing the contact surface area d) increasing the contact surface area e) increasing the weight of the block

6. 3. 3. A brick is resting on the surface of a flat board 6.3.3. A brick is resting on the surface of a flat board. As one end of the board is slowly raised, what changes, if any, are there in the normal force and in frictional forces exerted on the brick? a) The normal force increases as the frictional force increases. b) The normal force decreases as the frictional force increases. c) The normal force remains constant as the frictional force increases. d) Only the direction of the normal force changes as the direction of the frictional force changes. e) The normal force decreases; and the frictional force remains constant.

6. 3. 3. A brick is resting on the surface of a flat board 6.3.3. A brick is resting on the surface of a flat board. As one end of the board is slowly raised, what changes, if any, are there in the normal force and in frictional forces exerted on the brick? a) The normal force increases as the frictional force increases. b) The normal force decreases as the frictional force increases. c) The normal force remains constant as the frictional force increases. d) Only the direction of the normal force changes as the direction of the frictional force changes. e) The normal force decreases; and the frictional force remains constant.

6. 3. 4. A brick is resting on the surface of a flat board 6.3.4. A brick is resting on the surface of a flat board. One end of the board is slowly raised. The brick begins sliding down the board when it makes an angle  with respect to the horizontal plane. Which of the following give the correct expression of the coefficient of friction in this situation? a) mg sin  b) mg cos  c) sin  d) cos  e) tan 

6. 3. 4. A brick is resting on the surface of a flat board 6.3.4. A brick is resting on the surface of a flat board. One end of the board is slowly raised. The brick begins sliding down the board when it makes an angle  with respect to the horizontal plane. Which of the following give the correct expression of the coefficient of friction in this situation? a) mg sin  b) mg cos  c) sin  d) cos  e) tan 

6.4.1. The drag force is not dependent on which of the following parameters? a) air density b) the drag coefficient c) the speed of the object relative to the fluid in which it’s moving d) the terminal velocity e) cross-sectional area

6.4.1. The drag force is not dependent on which of the following parameters? a) air density b) the drag coefficient c) the speed of the object relative to the fluid in which it’s moving d) the terminal velocity e) cross-sectional area

6.4.2. Which one of the following has the largest terminal velocity? a) raindrop b) tennis ball c) ping pong ball d) parachutist with an open chute e) a shot put ball

6.4.2. Which one of the following has the largest terminal velocity? a) raindrop b) tennis ball c) ping pong ball d) parachutist with an open chute e) a shot put ball

6.4.3. The terminal velocity is not dependent on which one of the following properties? a) the force of gravity b) air density c) the falling time d) cross-sectional area e) the drag coefficient

6.4.3. The terminal velocity is not dependent on which one of the following properties? a) the force of gravity b) air density c) the falling time d) cross-sectional area e) the drag coefficient

6.5.1. When using the term “uniform circular motion,” what do we mean by the term “uniform?” a) The direction of the object’s velocity is constant. b) The net force on the moving object is zero newtons. c) The forces acting on the object are uniformly applied from all directions. d) The motion occurs without the influence of the gravitational force. e) The motion of the object is at a constant speed.

6.5.1. When using the term “uniform circular motion,” what do we mean by the term “uniform?” a) The direction of the object’s velocity is constant. b) The net force on the moving object is zero newtons. c) The forces acting on the object are uniformly applied from all directions. d) The motion occurs without the influence of the gravitational force. e) The motion of the object is at a constant speed.

6.5.2. If an object is moving in uniform circular motion, its period is given by which one of the following quantities? a) the speed of the object b) the centripetal acceleration of the object c) the number of revolutions the object makes each second d) the time interval for the object to make one revolution e) the displacement of the object

6.5.2. If an object is moving in uniform circular motion, its period is given by which one of the following quantities? a) the speed of the object b) the centripetal acceleration of the object c) the number of revolutions the object makes each second d) the time interval for the object to make one revolution e) the displacement of the object

6.5.3. A bicycle racer is traveling at constant speed v around a circular track. The centripetal acceleration of the bicycle is ac. What happens to the centripetal acceleration of the bicycle if the speed is doubled to 2v? a) The centripetal acceleration increases to 4ac. b) The centripetal acceleration decreases to 0.25ac. c) The centripetal acceleration increases to 2ac. d) The centripetal acceleration decreases to 0.5ac. e) The centripetal acceleration does not change.

6.5.3. A bicycle racer is traveling at constant speed v around a circular track. The centripetal acceleration of the bicycle is ac. What happens to the centripetal acceleration of the bicycle if the speed is doubled to 2v? a) The centripetal acceleration increases to 4ac. b) The centripetal acceleration decreases to 0.25ac. c) The centripetal acceleration increases to 2ac. d) The centripetal acceleration decreases to 0.5ac. e) The centripetal acceleration does not change.

6. 5. 4. A satellite orbits the Earth in uniform circular motion 6.5.4. A satellite orbits the Earth in uniform circular motion. What is the direction of centripetal acceleration of the satellite? a) The centripetal acceleration is a scalar quantity and it doesn’t have a direction. b) The centripetal acceleration vector points radially outward from the Earth. c) The centripetal acceleration vector points radially inward toward the Earth. d) The centripetal acceleration vector points in the direction of the satellite’s velocity. e) The centripetal acceleration vector points in the direction opposite that of the satellite’s velocity.

6. 5. 4. A satellite orbits the Earth in uniform circular motion 6.5.4. A satellite orbits the Earth in uniform circular motion. What is the direction of centripetal acceleration of the satellite? a) The centripetal acceleration is a scalar quantity and it doesn’t have a direction. b) The centripetal acceleration vector points radially outward from the Earth. c) The centripetal acceleration vector points radially inward toward the Earth. d) The centripetal acceleration vector points in the direction of the satellite’s velocity. e) The centripetal acceleration vector points in the direction opposite that of the satellite’s velocity.

6.5.5. A motorcycle travels at a constant speed around a circular track. Which one of the following statements about this motorcycle is true? a) The car has a velocity vector that points along the radius of the circle. b) The car is characterized by constant velocity. c) The car is characterized by constant acceleration. d) The velocity of the car is changing. e) The car has an acceleration vector that is tangent to the circle at all times.

6.5.5. A motorcycle travels at a constant speed around a circular track. Which one of the following statements about this motorcycle is true? a) The car has a velocity vector that points along the radius of the circle. b) The car is characterized by constant velocity. c) The car is characterized by constant acceleration. d) The velocity of the car is changing. e) The car has an acceleration vector that is tangent to the circle at all times.

6.5.6. The centripetal force is best explained by which of the following statements? a) The centripetal force is the force on an object that is directed radially outward from the center of its orbit. b) The centripetal force is the force on an orbiting object that is directed along a line that is tangent to the circle. c) The centripetal force is the net force acting on an orbiting object that maintains it in uniform circular motion. d) The centripetal force is a fundamental force of nature.

6.5.6. The centripetal force is best explained by which of the following statements? a) The centripetal force is the force on an object that is directed radially outward from the center of its orbit. b) The centripetal force is the force on an orbiting object that is directed along a line that is tangent to the circle. c) The centripetal force is the net force acting on an orbiting object that maintains it in uniform circular motion. d) The centripetal force is a fundamental force of nature.

6.5.7. Which one of the following forces holds a car on a frictionless banked curve? a) the horizontal component of the normal force b) the vertical component of the car's weight c) the vertical component of the normal force d) the horizontal component of the car's weight e) the reaction force to the car's weight

6.5.7. Which one of the following forces holds a car on a frictionless banked curve? a) the horizontal component of the normal force b) the vertical component of the car's weight c) the vertical component of the normal force d) the horizontal component of the car's weight e) the reaction force to the car's weight