CHAPTER 6 REVIEW NAME 1) Can work be done on a system if there is no motion? A) Yes, if an outside force is provided. B) Yes, since motion is only relative. C) No, since a system which is not moving has no energy. D) No, because of the way work is defined. Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.1 3) If you push twice as hard against a stationary brick wall, the amount of work you do A) doubles. B) is cut in half. C) remains constant but non-zero. D) remains constant at zero. Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.1 4) A 50-N object was lifted 2.0 m vertically and is being held there. How much work is being done in holding the box in this position? A) more than 100 J B) 100 J C) less than 100 J, but more than 0 J D) 0 J Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.1 3) If you walk 5.0 m horizontally forward at a constant velocity carrying a 10-N object, the amount of work you do is A) more than 50 J. B) equal to 50 J. C) less than 50 J, but more than 0 J. D) zero. Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.1 4) Does the centripetal force acting on an object do work on the object? A) Yes, since a force acts and the object moves, and work is force times distance. B) Yes, since it takes energy to turn an object. C) No, because the object has constant speed. D) No, because the force and the displacement of the object are perpendicular. Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.1 6) You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down. A) Work is + on the way up and + on the way down. B) Work is + on the way up and - on the way down. C) Work is - on the way up and + on the way down. D) Work is - on the way up and - on the way down. Answer: C Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.1
6) The area under the curve, on a Force versus position (F vs. x) graph, represents A) work. B) kinetic energy. C) power. D) potential energy. Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.2 7) The quantity 1/2 mv2 is A) the kinetic energy of the object. B) the potential energy of the object. C) the work done on the object by the force. 8) If the net work done on an object is positive, then the object's kinetic energy A) decreases. B) remains the same. C) increases. D) is zero. Answer: C 9) If the net work done on an object is negative, then the object's kinetic energy A) decreases. B) remains the same. C) increases. D) is zero. 10) If the net work done on an object is zero, then the object's kinetic energy A) decreases. B) remains the same. C) increases. D) is zero. 11) An object hits a wall and bounces back with half of its original speed. What is the ratio of the final kinetic energy to the initial kinetic energy? A) 1/2 B) 1/4 C) 2 D) 4 Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.3 12) You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions? A) It would have skidded 4 times farther. B) It would have skidded twice as far. C) It would have skidded 1.4 times farther.
D) It is impossible to tell from the information given. Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.3 13) A planet of constant mass orbits the Sun in an elliptical orbit. Neglecting any friction effects, what happens to the planet's kinetic energy? A) It remains constant. B) It increases continually. C) It decreases continually. D) It increases when the planet approaches the Sun, and decreases when it moves farther away. Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.3 14) The quantity mgy is A) the kinetic energy of the object. B) the gravitational potential energy of the object. C) the work done on the object by the force. Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.4-6.5 15) The quantity 1/2 kx2 is A) the kinetic energy of the object. B) the elastic potential energy of the object. C) the work done on the object by the force. Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.4-6.5 16) An acorn falls from a tree. Compare its kinetic energy K, to its potential energy U. A) K increases and U decreases. B) K decreases and U decreases. C) K increases and U increases. D) K decreases and U increases. Diff: 1 Type: BI Var: 1 Page Ref: Sec. 6.6-6.7 17) A ball falls from the top of a building, through the air (air friction is not present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building? A) K is equal to U. B) K is greater than U. C) K is less than U. D) It is impossible to tell. Diff: 2 Type: BI Var: 1 Page Ref: Sec. 6.8-6.9 18) A ball falls from the top of a building, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building? A) K is equal to U. B) K is greater than U. C) K is less than U. D) It is impossible to tell. Answer: C
19) The quantity Fd/t is 20) A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the 5500 N force? A) 2.75 105 J (W=Fd cosθ=f. d) 21) A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the weight of the elevator? B) -2.45 105 J (W=F. d=mgh) 22) A 4.00-kg box of fruit slides 8.0 m down a ramp, inclined at 30.0 from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box? A) 157 J (W =F. d, F= F x= mgsinθ, d=8) ) or (W=Fd cosθ, F=mg, θ=90-30, d=8) 23) A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the cart? B) 2.0 103 J (ΣW=ΔKE= F. d) 24) A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speed of the cart? C) 8.5 m/s (ΣW=ΔKE= F. d=½mv 2 ) 25) A 10-kg mass is moving with a speed of 5.0 m/s. How much work is required to stop the mass? D) 125 J (ΣW=ΔKE=½mv 2 ) 26) A spring-driven dart gun propels a 10-g dart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assuming the spring has negligible mass? B) 14 m/s (ΣW=ΔKE= F. d=½mv 2 ) 27) An arrow of mass 20 g is shot horizontally into a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping force acting on the arrow? C) 180 N (F. d=½mv 2 ) (ΣW=ΔKE) 28) A 400-N box is pushed up an inclined plane. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much work was done by the push? B) 800 J (mgh) (ΣW =GPE) 29) A spring is characterized by a spring constant of 60 N/m. How much potential energy does it store, when stretched by 1.0 cm? A) 3.0 10-3 J (½kx 2 =EPE)
30) A 60-kg skier starts from rest from the top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slope? (Neglect friction.) B) 31 m/s (½mv 2 =mgh) (ΔKE=GPE) FIGURE 6-2 31) A roller coaster starts from rest at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the dip? B) 17 m/s (½mv 2 =mgδh) (ΔKE=ΔGPE) 32) What is the minimum speed of the ball at the bottom of its swing (point B) in order for it to reach point A, which is 1.0-m above the bottom of the swing? FIGURE 6-3 C) 4.4 m/s (½mv 2 =mgδh) (ΔKE=ΔGPE) 33) A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal spring with spring constant of 2.0 106 N/m. What is the maximum compression of the spring? (Neglect the mass of the spring.) D) 0.68 m (½mv 2 =½kx 2 ΔKE =EPE)
34) A 60-kg skier starts from rest from the top of a 50-m high slope. If the work done by friction is -6.0 103 J, what is the speed of the skier on reaching the bottom of the slope? C) 28 m/s (ΣW=ΔKE) (ΣW=mgh-W f= ½mv 2 ) 35) At what rate is a 60.0-kg boy using energy when he runs up a flight of stairs 10.0-m high, in 8.00 s? B) 735 W (P=W/t=mgh/t) 36) A 10-N force is needed to move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by the force? C) 50 W P=W/t=Fv 37) A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the average power delivered by the engine? (1 hp = 746 W) D) 90 hp (P=W/t) (ΣW=ΔKE½mv 2 )