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A 25 N block rests on an adjustable inclined plane; the maximum angle just before it slips is 37° with the horizontal. What is the coefficient of static.

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Presentation on theme: "A 25 N block rests on an adjustable inclined plane; the maximum angle just before it slips is 37° with the horizontal. What is the coefficient of static."— Presentation transcript:

1 A 25 N block rests on an adjustable inclined plane; the maximum angle just before it slips is 37° with the horizontal. What is the coefficient of static friction between block and plane surfaces?

2 A 5000 N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T 1. Cable 2 applies a force upward and to the left at an angle of 37° to the negative x-axis and has a tension, T 2. What is the tension, T 1 ? N N N N

3 A 5000 N weight is held suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right of the object and has a tension, T 1. Cable 2 applies a force upward and to the left at an angle of 37° to the negative x-axis and has a tension, T 2. What is the tension, T 2 ? N N N N

4 A trapeze artist, with swing, weighs 800 N; he is being held to one side by his partner so that the swing ropes make an angle of 30° with the vertical. In such a condition of static equilibrium what is the tension in the rope? N N N N

5 As a 3.0 kg bucket is being lowered into a 10 m deep well, starting from the top, the tension in the rope is 9.8 N. The acceleration of the bucket will be m/s 2 downward m/s 2 downward 3.zero m/s 2 upward

6 A 70-kg man jumps a distance of 1 m down onto a concrete walkway. His downward motion stops in 0.02 seconds. If he forgets to bend his knees, what force is transmitted to his leg bones? ,490 N 2.7,010 N 3.4,900 N 4.3,500 N

7 A man pulls a sled at a constant velocity across a horizontal snow surface. If a force of 80 N is being applied to the sled rope at an angle of 53° to the ground, what is the force of friction between sled and snow? N 2.64 N 3.48 N 4.40 N

8 A trapeze artist, with swing, weighs 800 N; he is momentarily held to one side by his partner so that the swing ropes make an angle of 30° with the vertical. In such a condition of static equilibrium what is the horizontal force being applied by the partner? N N N N

9 There are six books in a stack, each with weight 5 N. The coefficient of friction between all the books is 0.2. With what horizontal force must I push to start sliding the fifth book out of the stack, leaving the top four and the sixth book behind? N N N N

10 A car goes forward along a level road at constant velocity. The total force acting on the tires is greater than the normal force times the coefficient of static friction. 2.equal to the normal force times the coefficient of static friction. 3.the normal force times the coefficient of kinetic friction. 4.zero.

11 As a car skids with its wheels locked trying to stop on a road covered with ice and snow, the force of friction between the icy road and the tires will usually be greater than the normal force of the road times the coefficient of static friction. 2.equal to the normal force of the road times the coefficient of static friction. 3.less than the normal force of the road times the coefficient of static friction. 4.greater than the normal force of the road times the coefficient of kinetic friction.

12 There are six books in a stack, each with a weight of 5 N. The coefficient of friction between all the books is 0.2. With what horizontal force must I push to start sliding the top five books off the bottom one? N N N N

13 As a car goes up a hill, there is a force of friction between the road and the tires rolling on the road. The maximum force of friction is equal to the weight of the car times the coefficient of kinetic friction. 2.the normal force of the road times the coefficient of kinetic friction. 3.the normal force of the road times the coefficient of static friction. 4.zero.

14 What condition must apply to a system's state of motion in order for it to be regarded as an inertial frame of reference? in decreasing velocity 2.in constant velocity 3.in constant acceleration 4.in increasing acceleration

15 A 2000 kg sailboat experiences an eastward force of 3000 N by the ocean tide and a wind force against its sails with magnitude of 6000 N directed toward the northwest (45° N of W). What is the magnitude of the resultant acceleration? m/s m/s m/s m/s 2

16 A 2000 kg sailboat experiences an eastward force of 3000 N by the ocean tide and a wind force against its sails with magnitude of 6000 N directed toward the northwest (45° N of W). What is the direction of the resultant acceleration? ° N of E 2.30° N of W 3.30° N of E 4.74° N of W

17 A wagon of weight 300 N is accelerated across a level surface at 0.5 m/s 2. What net force acts on the wagon? (g = 9.8 m/s 2 ) N 2.15 N N N

18 The statement by Newton that "for every action there is an opposite but equal reaction" is regarded as which of his laws of motion? first 2.second 3.third 4.fourth

19 A block having a mass of 5.0 kg rests on a horizontal surface where the coefficient of sliding kinetic friction between the two is 0.2. A string, attached to the block, is pulled horizontally resulting in a 2 m/s 2 acceleration by the block. What is the tension in the string? (g = 9.8 m/s 2 ) N N N 4.10 N

20 Two blocks of masses 6 and 9 kg, respectively, rest on a frictionless horizontal surface and are attached by a string. A second string, attached only to the 9 kg block, has a horizontal force of 30 N applied to it, causing both blocks to accelerate. What is the tension in the string between the two blocks? N 2.28 N 3.12 N 4.15 N

21 If it is known that a net force is acting on an object, then which of the following must be assumed regarding the object's condition? The object is at rest. 2.moving with a constant velocity. 3.being accelerated. 4.losing mass.

22 The statement by Newton that "an object in motion tends to remain in motion" is regarded as which of his laws of motion? first 2.second 3.third 4.fourth

23 The acceleration due to gravity on the surface of planet Q is three times that on the Earth. Thus an object with a measured mass of 5.0 kg on Earth would have what mass on planet Q? kg 2.45 kg kg 4.5 kg

24 A 9 kg hanging weight is connected by a string over a pulley to a 5 kg block sliding on a flat table. If the coefficient of sliding friction is 0.2, find the tension in the string N N N N

25 The coefficient of static friction between the tires of a car and the street is µ s = What is the steepest angle of a street q, on which a car can be parked (with wheels locked) without slipping? ° 2.30° 3.37° 4.45°

26 A baseball batsman strikes an incoming 40 m/s fastball. The ball leaves the bat at 50 m/s after a ball-on-bat contact time of 0.03 s. What is the force exerted on the 0.15 kg baseball? N N N 4.90 N

27 An ice skater moving at 10 m/s coasts to a halt in 100 m on a smooth ice surface. What is the coefficient of friction between the ice and the skates? µ = µ = µ = µ = 0.205

28 An Olympic skier moving at 20 m/s down a 30° slope encounters a region of wet snow, of coefficient of friction µ k = How far down the slope does she go before coming to a halt? m m m m

29 Find the tension in an elevator cable if the 1000 kg elevator is descending with an acceleration of 1.8 m/s 2, downward ,700 N 2.8,000 N 3.9,800 N 4.11,600 N

30 A shotputter moves his arm and the 7 kg shot through a distance of 1 meter. If the shot is given a velocity of 10 m/s from rest, find the average force exerted on the shot during this time N N N N

31 The accelerating force of the wind on a small 200 kg sailboat is 707 N northeast. If the drag of the keel is 500 N acting west, what is the acceleration of the boat? m/s 2 due East m/s 2 due North m/s 2 Northeast m/s 2 North by Northwest

32 A barefoot field-goal kicker imparts a velocity of 30 m/s to a football at rest. If the football has a mass of 0.5 kg and time-of-contact with the football is s, what is the force exerted on the foot? N N N N

33 A worker pulls a 200 N packing crate at constant velocity across a rough floor by exerting a force F = 55 N at an angle of 35° above the horizontal. What is the coefficient of kinetic friction of the floor?

34 An automobile of mass 2000 kg moving at 30 m/s, is braked suddenly, with a constant braking force of 10,000 N. How far does the car travel before stopping? m 2.90 m m m

35 A karate-master strikes a board with an initial velocity of 10 m/s, decreasing to 1 m/s as his hand passes through the board. If the time-of-contact with the board is s, and the mass of the coordinated hand and arm is 1 kg, what is the force exerted on the board? N N N N

36 A girl is using a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30° above the horizontal and the tension in the rope is 100 N. What is the normal force of the floor on the box? N 2.86 N 3.50 N N

37 A girl is using a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30° above the horizontal and the tension in the rope is 100 N. What is the coefficient of friction?

38 A crate is carried in a pickup truck traveling horizontally at 15 m/s. If the coefficient of static friction between the crate and the truckbed is 0.40, what is the minimum stopping distance for the truck so the crate will not slide? m m m m

39 A 20-kg traffic light hangs midway on a cable between two poles 40 meters apart. If the sag in the cable is 0.4 meters, what is the tension in each side of the cable? ,000 N 2.9,800 N 3.4,900 N N

40 Assume the coefficient of friction between the wheels of a racecar and the track is 1. If the car starts from rest and accelerates at a constant rate for 400 m (1/4 mile), what is its velocity at the end of the race? m/s 2.66 m/s 3.88 m/s 4.99 m/s

41 A 300 kg crate is placed on an adjustable inclined plane. As one end of the incline is raised, the crate begins to move downward. If the crate slides down the plane with an acceleration of 0.7 m/s 2 when the incline angle is 25°, what is the coefficient of kinetic friction between ramp and crate? (g = 9.8 m/s 2 )

42 A 250 kg crate is placed on an adjustable inclined plane. If the crate slides down the incline with an acceleration of 0.7 m/s 2 when the incline angle is 25°, then what should the incline angle be in order for the crate to slide down the plane at constant speed? (g = 9.8 m/s 2 ) ° 2.21° 3.25° 4.29°

43 A puck, upon being struck by a hockey stick, is given an initial speed of 8 m/s and continues to move in a straight path for a distance of 16 m before coming to rest. What is the negative rate of acceleration? m/s m/s m/s m/s 2

44 A 300 kg crate is placed on an adjustable inclined plane. As one end of the incline is raised, the crate begins to move downward just as the angle of inclination reaches 25°. What is the coefficient of static friction between crate and incline surface?

45 A 15 kg block rests on a level frictionless surface and is attached by a light string to a 5.0 kg hanging mass where the string passes over a massless frictionless pulley. If g = 9.8 m/s 2, what is the tension in the connecting string? N 2.17 N 3.49 N N

46 A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250 kg crate. If g = 9.8 m/s 2, what is the coefficient of static friction?

47 A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250 kg crate. What is the acceleration of the crate if the 800 N force is maintained after the crate begins to move and the coefficient of kinetic friction is 0.12? m/s m/s m/s m/s 2

48 A 15 kg block and a 5.0 kg hanging mass are connected by a light string over a massless frictionless pulley. If g = 9.8 m/s 2, what is the acceleration of the system when released? m/s m/s m/s m/s 2

49 An object of what mass acted upon by a net force of 20 N will experience an acceleration of 10 m/s 2 ? kg kg kg 4.10 kg

50 Which of the following is an example of the type of force which acts at a distance? gravitational 2.magnetic 3.electrical 4.all of these

51 An object of mass 25 kg acted upon by a net force of 10 N will experience what acceleration? m/s m/s m/s m/s 2

52 Which of the following expresses a principle which was initially stated by Galileo and was later incorporated into Newton's laws of motion? An object's acceleration is inversely proportional to its mass. 2.For every action there is an equal but opposite reaction. 3.The natural condition for a moving object is to remain in motion. 4.The natural condition for a moving object is to come to rest.

53 Two perpendicular forces, one of 45 N directed due north and the second, 60 N directed due east, act simultaneously on an object with mass of 35 kg. What is the resultant acceleration of the object? m/s m/s m/s m/s 2

54 An airplane of mass 1.2 x 10 4 kg tows a glider of mass 0.6 x 10 4 kg. If the airplane propellers provide a net forward thrust of 3.6 x 10 4 N, what is the acceleration of the glider? m/s m/s m/s m/s 2

55 Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8 kg mass is another light string which a person uses to pull both blocks horizontally. If the two block system accelerates at 0.5 m/s 2, then what is the tension in the connecting string between the blocks? N 2.6 N 3.10 N N

56 Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8 kg mass is another light string which a person uses to pull both blocks horizontally. If the two block system accelerates at 0.5 m/s 2, what is the tension in the string attached to the 8 kg mass? N 2.6 N 3.10 N N

57 A sled weighing 100 N is held in place on a frictionless 20 degree slope by a rope attached to a stake at the top. The rope is parallel to the slope. What is the normal force of the slope acting on the sled? N 2.47 N 3.37 N 4.34 N

58 A 150 N sled is pulled up a 28 degree slope at a constant speed by a force of 100 N. What is the coefficient of kinetic friction between sled and slope?

59 A 150 N sled is pulled up a 28 degree slope at a constant speed by a force of 100 N. Near the top of the hill the sled is released. With what acceleration does the sled go back down the hill? m/s m/s m/s m/s

60 A 500 N tightrope walker stands at the center of the rope such that each half of the rope makes an angle of 10° with the horizontal. What is the tension in the rope? N N N N

61 A sled weighing 100 N is held in place on a frictionless 20 degree slope by a rope attached to a stake at the top. The rope is parallel to the slope. What is the tension in the rope? N 2.47 N 3.37 N 4.34 N

62 A 500 N tightrope walker stands at the center of the rope. If the rope can withstand a tension of 1800 N without breaking, what is the minimum angle the rope can make with the horizontal? ° 2.8° 3.10° 4.15°

63 As a basketball player starts to jump for a rebound, he begins to move upward faster and faster until he leaves the floor. During this time that he is in contact with the floor, the force of the floor on his shoes is bigger than his weight. 2.equal in magnitude and opposite in direction to his weight. 3.less than his weight. 4.zero.

64 As I slide a box at constant speed up a frictionless slope, pulling parallel to the slope, the tension in the rope will be greater than the tension would be if the box were stationary. 2.greater than the weight of the box. 3.equal to the weight of the box. 4.less than the weight of the box.

65 A boxcar of mass 200 tons at rest becomes uncoupled on a 10° grade. If the track is considered to be frictionless, what velocity does the boxcar have after 10 seconds? m/s 2.9 m/s 3.13 m/s 4.17 m/s

66 A thrown brick hits a window, breaking the glass, and ends up on the floor inside the room. Since the brick broke the glass, we know that the force of the brick on the glass was bigger than the force of the glass on the brick. 2.the force of the brick on the glass was the same size as the force of the glass on the brick. 3.the force of the brick on the glass was less than the force of the glass on the brick. 4.the brick didn't slow down as it broke the glass.

67 A soccer player accelerates a 0.4 kg ball from rest to a speed of 9 m/s during the 0.15 s of time in which his foot is in contact with the ball. What average force is applied to the ball during the kick? N 2.72 N 3.24 N 4.60 N

68 An elevator weighing 20,000 N is supported by a steel cable. What is the tension in the cable when the elevator is being accelerated upward at a rate of 3.0 m/s 2 ? (g = 9.8 m/s 2 ) ,900 N 2.23,100 N 3.20,000 N 4.26,100 N

69 It is past midnight and Sue is sliding down a rope from her third floor window to meet her boyfriend. As she slides down the rope faster and faster, she becomes frightened and grabs harder on the rope, increasing the tension in the rope. As soon as the upward tension in the rope becomes equal to Sue's weight, Sue will stop. 2.Sue will slow down. 3.Sue will continue down at a constant velocity. 4.the rope must break.

70 A hockey puck struck by a hockey stick is given an initial velocity of 10 m/s. If the coefficient of kinetic friction between ice and puck is 0.1, how far will the puck slide before stopping? m 2.45 m 3.51 m 4.57 m


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