Chapter 4 Quick Check Problems Quick Check 4

Chapter 4 Quick Check Problems

Quick Check 4. 1 The net force on an object points to the left. Two of three forces are shown. Which is the missing third force? A. © 2015 Pearson Education, Inc. B. C. D.

Quick Check 4. 1 The net force on an object points to the left. Two of three forces are shown. Which is the missing third force? A. © 2015 Pearson Education, Inc. B. C. D.

Quick Check 4. 2 A ball rolls down an incline and off a horizontal ramp. Ignoring air resistance, what force or forces act on the ball as it moves through the air just after leaving the horizontal ramp? A. The weight of the ball acting vertically down. B. A horizontal force that maintains the motion. C. A force whose direction changes as the direction of motion changes. D. The weight of the ball and a horizontal force. E. The weight of the ball and a force in the direction of motion. © 2015 Pearson Education, Inc.

Quick Check 4. 3 A steel beam hangs from a cable as a crane lifts the beam. What forces act on the beam? A. Gravity B. Gravity and tension in the cable C. Gravity and a force of motion D. Gravity and tension and a force of motion © 2015 Pearson Education, Inc.

Quick Check 4. 4 A bobsledder pushes her sled across horizontal snow to get it going, then jumps in. After she jumps in, the sled gradually slows to a halt. What forces act on the sled just after she’s jumped in? A. B. C. D. E. Gravity and kinetic friction Gravity and a normal force Gravity and the force of the push Gravity, a normal force, and kinetic friction Gravity, a normal force, kinetic friction, and the force of the push © 2015 Pearson Education, Inc.

Quick Check 4. 5 A cart is pulled to the right with a constant, steady force. How will its acceleration graph look? A. © 2015 Pearson Education, Inc. B. C.

Quick Check 4. 6 A constant force causes an object to accelerate at 4 m/s 2. What is the acceleration of an object with twice the mass that experiences the same force? A. 1 m/s 2 B. 2 m/s 2 C. 4 m/s 2 D. 8 m/s 2 E. 16 m/s 2 © 2015 Pearson Education, Inc.

Quick Check 4. 7 An object, when pushed with a net force F, has an acceleration of 2 m/s 2. Now twice the force is applied to an object that has four times the mass. Its acceleration will be A. ½ m/s 2 B. 1 m/s 2 C. 2 m/s 2 D. 4 m/s 2 © 2015 Pearson Education, Inc.

Quick Check 4. 8 A 40 -car train travels along a straight track at 40 mph. A skier speeds up as she skis downhill. On which is the net force greater? A. The train B. The skier C. The net force is the same on both. D. There’s not enough information to tell. © 2015 Pearson Education, Inc.

Quick Check 4. 9 An object on a rope is lowered at constant speed. Which is true? A. The rope tension is greater than the object’s weight. B. The rope tension equals the object’s weight. C. The rope tension is less than the object’s weight. D. The rope tension can’t be compared to the object’s weight. © 2015 Pearson Education, Inc.

Quick Check 4. 10 An object on a rope is lowered at a steadily decreasing speed. Which is true? A. The rope tension is greater than the object’s weight. B. The rope tension equals the object’s weight. C. The rope tension is less than the object’s weight. D. The rope tension can’t be compared to the object’s weight. © 2015 Pearson Education, Inc.

Quick Check 4. 11 An elevator, lifted by a cable, is moving upward and slowing. Which is the correct free-body diagram? A. © 2015 Pearson Education, Inc. B. C. D. E.

Quick Check 4. 12 A ball has been tossed straight up. Which is the correct free-body diagram just after the ball has left the hand? Ignore air resistance. © 2015 Pearson Education, Inc. A. B. C. D.

Quick Check 4. 13 A ball, hanging from the ceiling by a string, is pulled back and released. Which is the correct free-body diagram just after its release? A. © 2015 Pearson Education, Inc. B. C. D. E.

Quick Check 4. 14 A car is parked on a hill. Which is the correct free-body diagram? © 2015 Pearson Education, Inc.

Quick Check 4. 15 A car is towed to the right at constant speed. Which is the correct free-body diagram? © 2015 Pearson Education, Inc.

Quick Check 4. 17 A mosquito runs head-on into a truck. Splat! Which is true during the collision? A. The mosquito exerts more force on the truck than the truck exerts on the mosquito. B. The truck exerts more force on the mosquito than the mosquito exerts on the truck. C. The mosquito exerts the same force on the truck as the truck exerts on the mosquito. D. The truck exerts a force on the mosquito but the mosquito does not exert a force on the truck. E. The mosquito exerts a force on the truck but the truck does not exert a force on the mosquito. © 2015 Pearson Education, Inc.

Chapter 5 Quick Check Problems

Quick Check 5. 1 A ring, seen from above, is pulled on by three forces. The ring is not moving. How big is the force F? A. 20 N B. 10 cos N C. 10 sin N D. 20 cos N E. 20 sin N © 2015 Pearson Education, Inc.

Quick Check 5. 4 What are the components of system shown? © 2015 Pearson Education, Inc. in the coordinate

Quick Check 5. 5 A 50 -kg student (mg = 490 N) gets in a 1000 -kg elevator at rest and stands on a metric bathroom scale. As the elevator accelerates upward, the scale reads A. > 490 N B. 490 N C. < 490 N but not 0 N D. 0 N © 2015 Pearson Education, Inc.

Quick Check 5. 6 A 50 -kg student (mg = 490 N) gets in a 1000 -kg elevator at rest and stands on a metric bathroom scale. Sadly, the elevator cable breaks. What is the reading on the scale during the few seconds it takes the student to plunge to his doom? A. > 490 N B. 490 N C. < 490 N but not 0 N D. 0 N © 2015 Pearson Education, Inc.

Quick Check 5. 2 The box is sitting on the floor of an elevator. The elevator is accelerating upward. The magnitude of the normal force on the box is A. B. C. D. E. n > mg n = mg n < mg n=0 Not enough information to tell © 2015 Pearson Education, Inc.

Quick Check 5. 3 A box is being pulled to the right at steady speed by a rope that angles upward. In this situation: A. n > mg B. n = mg C. n < mg D. n = 0 E. Not enough information to judge the size of the normal force © 2015 Pearson Education, Inc.

Quick Check 5. 7 A box on a rough surface is pulled by a horizontal rope with tension T. The box is not moving. In this situation: A. B. C. D. E. fs > T fs = T fs < T fs = smg fs = 0 © 2015 Pearson Education, Inc.

Quick Check 5. 8 A box with a weight of 100 N is at rest. It is then pulled by a 30 N horizontal force. Does the box move? A. Yes B. No C. Not enough information to say © 2015 Pearson Education, Inc.

Quick Check 5. 9 A box is being pulled to the right over a rough surface. T > fk, so the box is speeding up. Suddenly the rope breaks. What happens? The box A. B. C. D. E. Stops immediately. Continues with the speed it had when the rope broke. Continues speeding up for a short while, then slows and stops. Keeps its speed for a short while, then slows and stops. Slows steadily until it stops. © 2015 Pearson Education, Inc.

Quick Check 5. 11 Consider the situation in the figure. Which pair of forces is an action/reaction pair? A. The tension of the string and the friction force acting on A B. The normal force on A due to B and the weight of A C. The normal force on A due to B and the weight of B D. The friction force acting on A and the friction force acting on B © 2015 Pearson Education, Inc.

Quick Check 5. 12 Boxes A and B are being pulled to the right on a frictionless surface; the boxes are speeding up. Box A has a larger mass than Box B. How do the two tension forces compare? A. B. C. D. T 1 > T 2 T 1 = T 2 T 1 < T 2 Not enough information © 2015 Pearson Education, Inc.

Quick Check 5. 13 Boxes A and B are sliding to the right on a frictionless surface. Hand H is slowing them. Box A has a larger mass than Box B. Considering only the horizontal forces: A. B. C. D. FB on H = FH on B = FA on B = FB on A FB on H = FH on B > FA on B = FB on A FB on H = FH on B < FA on B = FB on A FH on B = FH on A > FA on B © 2015 Pearson Education, Inc.

Quick Check 5. 10 All three 50 -kg blocks are at rest. The tension in rope 2 is A. Greater than the tension in rope 1. B. Equal to the tension in rope 1. C. Less than the tension in rope 1. © 2015 Pearson Education, Inc.

Quick Check 5. 15 The top block is accelerated across a frictionless table by the falling mass m. The string is massless, and the pulley is both massless and frictionless. The tension in the string is A. T < mg B. T = mg C. T > mg © 2015 Pearson Education, Inc.

Chapter 6 Quick Check Problems

Quick Check 3. 19 A car is traveling around a curve at a steady 45 mph. Is the car accelerating? A. Yes B. No © 2015 Pearson Education, Inc.

Quick Check 3. 20 A car is traveling around a curve at a steady 45 mph. Which vector shows the direction of the car’s acceleration? E. The acceleration is zero. © 2015 Pearson Education, Inc.

Quick Check 3. 21 A toy car moves around a circular track at constant speed. It suddenly doubles its speed — a change of a factor of 2. As a result, the centripetal acceleration changes by a factor of A. 1/4 B. 1/2 C. No change since the radius doesn’t change. D. 2 E. 4 © 2015 Pearson Education, Inc.

Quick Check 6. 6 An ice hockey puck is tied by a string to a stake in the ice. The puck is then swung in a circle. What force is producing the centripetal acceleration of the puck? A. B. C. D. E. Gravity Air resistance Friction Normal force Tension in the string © 2015 Pearson Education, Inc.

Quick Check 6. 7 A coin is rotating on a turntable; it moves without sliding. At the instant shown in the figure, which arrow gives the direction of the coin’s velocity? © 2015 Pearson Education, Inc.

Quick Check 6. 8 A coin is rotating on a turntable; it moves without sliding. At the instant shown in the figure, which arrow gives the direction of the frictional force on the coin? © 2015 Pearson Education, Inc.

Quick Check 6. 9 A coin is rotating on a turntable; it moves without sliding. At the instant shown, suppose the frictional force disappeared. In what direction would the coin move? © 2015 Pearson Education, Inc.

Conceptual Example 6. 4 Engineers design curves on roads to be segments of circles. They also design dips and peaks in roads to be segments of circles with a radius that depends on expected speeds and other factors. A car is moving at a constant speed and goes into a dip in the road. At the very bottom of the dip, which of the following is true? A. B. C. D. n>w n=w n<w Not enough information © 2015 Pearson Education, Inc.

Quick Check 6. 10 A physics textbook swings back and forth as a pendulum. Which is the correct free-body diagram when the book is at the bottom and moving to the right? © 2015 Pearson Education, Inc.

Quick Check 6. 11 A car that’s out of gas coasts over the top of a hill at a steady 20 m/s. Assume air resistance is negligible. Which free-body diagram describes the car at this instant? © 2015 Pearson Education, Inc.

Quick Check 6. 12 A roller coaster car does a loop-the -loop. Which of the free-body diagrams shows the forces on the car at the top of the loop? Rolling friction can be neglected. © 2015 Pearson Education, Inc.

Quick Check 6. 14 A coin sits on a turntable as the table steadily rotates counterclockwise. The free-body diagrams below show the coin from behind, moving away from you. Which is the correct diagram? © 2015 Pearson Education, Inc.