Clicker Question. A. 5 cm B. 10 cm C cm D. 20 cm E. 40 cm

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2 A block of mass m slides with speed v on a frictionless surface. It collides with an ideal spring and compresses it 10 cm before momentarily stopping. What is the max compression if the same mass has speed 2v initially? A. 5 cm B. 10 cm C cm D. 20 cm E. 40 cm

5 A block of mass m slides with speed v on a frictionless surface. It collides with an ideal spring and compresses it 10 cm before momentarily stopping. What is the max compression if a mass of 2m collides at speed v? A. 5 cm B. 10 cm C cm D. 20 cm E. 40 cm

6 You can throw a ball with speed vo. If you stand on the top of a building, in which case would the ball hit the ground with the highest speed vf? (Ignore air resistance.) A) When thrown straight up B) When thrown straight down C) When thrown horizontally D) All give the same speed when hitting the ground

7 You can throw a ball with speed vo. If you stand on the top of a building, in which case would the ball hit the ground with the highest speed vf? (Ignore air resistance.) A) When thrown straight up B) When thrown straight down C) When thrown horizontally D) All give the same speed when hitting the ground

8 Suppose you threw the ball straight up with speed vo. If you next want the ball to go twice as high, what is the new speed you need throw it with (ignore air resistance)? A. twice vo B. four times vo C. half of vo D. 2 times vo E. None of these

9 Suppose you threw the ball straight up with speed vo. If you next want the ball to go twice as high, what is the new speed you need throw it with (ignore air resistance)? A. twice vo B. four times vo C. half of vo D. 2 times vo E. None of these

10 A block of mass m rests on an ramp which makes angle θ with the horizontal. For the block and the ramp, the coefficient of static friction µs is larger than the coefficient of kinetic friction µk. What is the maximum force Fmax, that must be exerted on the block before it begins to move up the ramp? [b] [d] F max = 0 F max = mg( sin! + µ s cos! ) F max = mg( sin! " µ s cos! ) F max = mg sin! + µ k cos! ( ) [e] None of these θ Fmax

11 A block of mass m rests on an ramp which makes angle θ with the horizontal. For the block and the ramp, the coefficient of static friction µs is larger than the coefficient of kinetic friction µk. What is the maximum force Fmax, that must be exerted on the block before it begins to move up the ramp? [b] [d] F max = 0 F max = mg( sin! + µ s cos! ) F max = mg( sin! " µ s cos! ) F max = mg sin! + µ k cos! ( ) [e] None of these θ Fmax

12 An object of mass m is initially at rest at the top of a frictionless hill of height h as shown in the figure. What can be said about the properties of the object will it have when it reaches the bottom of the hill? The kinetic energy will equal the work done by gravity m [b] v = 2hg Potential energy is converted into kinetic energy h [d] a, b, and c are correct [e] None of these

13 An object of mass m is initially at rest at the top of a frictionless hill of height h as shown in the figure. What can be said about the properties of the object will it have when it reaches the bottom of the hill? The kinetic energy will equal the work done by gravity m [b] v = 2hg Potential energy is converted into kinetic energy h [d] a, b, and c are correct [e] None of these

14 In the figure, a block of mass 7.0 kg on a tabletop is attached by strings to vertically hanging masses, 12 kg and 10 kg, as shown. The strings and pulleys are massless, the pulleys are frictionless, but the coefficient of friction µk between the block and the tabletop is The magnitude and direction of the acceleration of the block is best described by: Not one of the listed answers [b] 9.81 m/s 2 to the left 4.40 m/s 2 to the left [d] 0.44 m/s 2 to the right [e] 0.44 m/s 2 to the left

15 In the figure, a block of mass 7.0 kg on a tabletop is attached by strings to vertically hanging masses, 12 kg and 10 kg, as shown. The strings and pulleys are massless, the pulleys are frictionless, but the coefficient of friction µk between the block and the tabletop is The magnitude and direction of the acceleration of the block is best described by: Not one of the listed answers [b] 9.81 m/s 2 to the left 4.40 m/s 2 to the left [d] 0.44 m/s 2 to the right [e] 0.44 m/s 2 to the left

16 In the figure, a 10-kg mass is suspended from two spring scales that read in kilograms, each of which has negligible weight. Thus: The top scale will read zero, the lower scale will read 10 kg. [b] Each scale will read 5 kg. The lower scale will read zero, the top scale will read 10 kg. [d] Each scale will read 10 kg. [e] Each scale will show a reading between one and 10 kg, such that the sum of the two is 10 kg. However, exact readings cannot be determined without more information.

17 In the figure, a 10-kg mass is suspended from two spring scales that read in kilograms, each of which has negligible weight. Thus: The top scale will read zero, the lower scale will read 10 kg. [b] Each scale will read 5 kg. The lower scale will read zero, the top scale will read 10 kg. [d] Each scale will read 10 kg. [e] Each scale will show a reading between one and 10 kg, such that the sum of the two is 10 kg. However, exact readings cannot be determined without more information.

18 In the figure, a constant external force P = 130 N is applied to a 20-kg box, which is on a rough horizontal surface. The force pushes the box a distance of 8.0 m, in a time interval of 4.0 s, and the speed changes from v1 = 0.5 m/s to v2 = 2.6 m/s. The work done by the external force P is closest to: +900 J [b] +810 J +720 J [d] -900 J [e] -810 J

19 In the figure, a constant external force P = 130 N is applied to a 20-kg box, which is on a rough horizontal surface. The force pushes the box a distance of 8.0 m, in a time interval of 4.0 s, and the speed changes from v1 = 0.5 m/s to v2 = 2.6 m/s. The work done by the external force P is closest to: +900 J [b] +810 J +720 J [d] -900 J [e] -810 J

20 The State Fair Midway Barrel of Fun must rotate with a certain minimum period in order for a rider of mass m1 to stick to the wall. How does this minimum rotation period change for a rider of mass m2 > m1? [b] [d] It must rotate faster with a shorter period It is the same It can rotate slower with a longer period Not enough information

21 The State Fair Midway Barrel of Fun must rotate with a certain minimum period in order for a rider of mass m1 to stick to the wall. How does this minimum rotation period change for a rider of mass m2 > m1? [b] [d] It must rotate faster with a shorter period It is the same It can rotate slower with a longer period Not enough information

22 A 12 N horizontal force is applied to a 40 N block on a rough horizontal surface. The block is initially at rest. If static friction coefficient is 0.5 and kinetic friction coefficient is 0.4, the frictional force on the block is (draw a diagram!): [b] [d] [e] 8 N 12 N 16 N 20 N 40 N

23 A 12 N horizontal force is applied to a 40 N block on a rough horizontal surface. The block is initially at rest. If static friction coefficient is 0.5 and kinetic friction coefficient is 0.4, the frictional force on the block is (draw a diagram!): [b] [d] [e] 8 N 12 N 16 N 20 N 40 N

24 An object of mass 1 kg is whirled in a horizontal circle of radius 0.5 m at a constant speed of 2 m/s. The work done on the object during one revolution is: [b] [d] [e] 0 J 1 J 2 J 4 J 16 J

25 An object of mass 1 kg is whirled in a horizontal circle of radius 0.5 m at a constant speed of 2 m/s. The work done on the object during one revolution is: [b] [d] [e] 0 J 1 J 2 J 4 J 16 J

26 Consider an object released at time initial-component of velocity, v x,o = 0 according to: t = 0 with an and accelerating a x = dv x = c 0 c 1 v x dt After a very long time, the x-component of the velocity is [b] v x = 0 v x = c 0 c 1 v = c c x 0 1 [d] v = c + c x 0 1 [e] None of these

27 Consider an object released at time initial-component of velocity, v x,o = 0 according to: t = 0 with an and accelerating a x = dv x = c 0 c 1 v x dt After a very long time, the x-component of the velocity is [b] v x = 0 v x = c 0 c 1 v = c c x 0 1 [d] v = c + c x 0 1 [e] None of these

28 An escalator is used to move 20 people (60 kg each) per minute from the first floor of a department store to the second floor, 5.0 m above. Neglect friction. The power required is approximately: [b] [d] [e] 100 W 200 W 1000 W 2000 W 60,000 W

29 An escalator is used to move 20 people (60 kg each) per minute from the first floor of a department store to the second floor, 5.0 m above. Neglect friction. The power required is approximately: [b] [d] [e] 100 W 200 W 1000 W 2000 W 60,000 W

30 A skier of mass M slides down a ski jump ramp shaped as a circle of radius R. At the end point of the ramp just before the skier is in the air, the magnitude of the normal force exerted by the ramp on the skier is n. Which of the following is true? top of ramp R end of ramp The magnitude of the normal force n is greater than gm. [b] The magnitude of the normal force n is equal to gm. The magnitude of the normal force n is less than gm. [d] The magnitude of the normal force n can be greater than, equal to, or less than gm depending on the speed. [e] None of the above statements are true.

31 A skier of mass M slides down a ski jump ramp shaped as a circle of radius R. At the end point of the ramp just before the skier is in the air, the magnitude of the normal force exerted by the ramp on the skier is n. Which of the following is true? top of ramp R end of ramp The magnitude of the normal force n is greater than gm. [b] The magnitude of the normal force n is equal to gm. The magnitude of the normal force n is less than gm. [d] The magnitude of the normal force n can be greater than, equal to, or less than gm depending on the speed. [e] None of the above statements are true.

32 Two circus clowns are launched from the same spring-loaded circus cannon, with the spring compressed the same distance each time. Clown A has a 40 kg mass and clown B has a 60 kg mass. The relation between their speeds at the instant of launch is v A = 3 2 v B [b] [d] [e]

33 Two circus clowns are launched from the same spring-loaded circus cannon, with the spring compressed the same distance each time. Clown A has a 40 kg mass and clown B has a 60 kg mass. The relation between their speeds at the instant of launch is v A = 3 2 v B [b] [d] [e]