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Semester 1 Physics Review Questions (part 2) Retzlaff 67) A ball rolls over the edge of a table with a horizontal velocity v m/s. The height of the table is 1.6 m and the horizontal range of the ball from the base of the table is 20 m. What is the initial speed of the ball? 68) A ball rolls over the edge of a table with a horizontal velocity v m/s. The height of the table is 1.6 m and the horizontal range of the ball from the base of the table is 20 m. What is the horizontal velocity of the ball just before it touches the ground? 69) A ball rolls off the edge of a table with an initial velocity of 20 m/s. The height of the table above the ground is 2.0 m. How long does it take the ball to reach the ground? 70) A bullet is fired from ground level with a speed of 150 m/s at an angle 30.0° above the horizontal. What is the vertical component of its velocity after 4 seconds? 71) A ball is thrown with an initial speed of 60. m/s at an angle of 30° above the horizontal. What is the ball's horizontal displacement at the end of 4 seconds? 72) A boy kicks a football with a certain initial velocity at an angle 20° above the horizontal. In 2.0 seconds, the ball reaches at its highest point in its trajectory. What is the initial velocity of the ball? 73) A boy kicks a football from ground level with an initial velocity of 20. m/s at an angle of 30° above the horizontal. What is the vertical component of its velocity at the highest point of its trajectory? 74) A boy kicks a football from ground level with an initial velocity of 20 m/s at an angle of 60° above the horizontal. What is the horizontal distance to the point where the football hits the ground? 75) A boy kicks a football with an initial velocity of 28.0 m/s at an angle of 30.0° above the horizontal. What is the highest elevation reached by the football in its trajectory? 76) A boy kicks a football from ground level with an initial velocity of 20. m/s at an angle of 30° above the horizontal. What is the horizontal component of its velocity at the highest point of its trajectory? 77) A crow is flying horizontally with a constant speed of 2.70 m/s when it releases a clam from its beak. The clam lands on the rocky beach 2.10 s later. Just before the clam lands, what is (a) its horizontal component of velocity, and (b) its vertical component of velocity? (c) its resultant velocity and the angle it makes below the horizontal? 78) A young girl swings on a rope above the local swimming hole (Figure 4-21). When she lets go of the rope her initial velocity is 2 .25 m/s at an angle of 35.0° above the horizontal. If she is in flight for 0.616 s, how high above the water was she when she let go of the rope? Figure 4-21 79) In the absence of an external unbalanced force, a moving object will do what as time goes on? 80) An object is moving with constant velocity. What can you say about the net force, friction, and the direction of the forces? 81) When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means what regarding forces? Draw a FBD 82) Race cars do not have airbags, but they do strap their helmets to the seat behind their head. Using the concept of inertial explain how this prevents neck injury? 83) A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. Given the damage to the car, how does the force on the truck relate to the force on the car? 84) A 8000kg truck is towing a 2000kg car. The force exerted by the truck on the car is 6000 N. The force exerted by the car on the truck is ________. 85) A 1.0kg golf club hits 100.g golf ball with a force of 2400 N. What is the force of the golf ball on the club? Figure 5-1 86) In Figure 5-1, masses m1 and m2 are such that m1> m2 and they lay on a level, frictionless surface. We can apply a horizontal force F either from the left or from the right. How do the contact force between the masses relate when pushing on m1 compared to pushing on m2? 87) A In Figure 5-1, masses m1= 34.4kg and m2= 19.6kg lay on a level, frictionless surface. We apply a horizontal force F = 5.63N to the left on m2. What is the contact force between the masses? 88) A ball is thrown up into the air. Ignore air resistance. When it is rising and reaches half of its maximum height, the net force acting on it is _______. 89) The elevator in the space needle accelerates downward. As it speeds up, the tension in the top cable is increased increasing the vertical force that is exerted on the elevator. When this force equals the weight of the elevator, what happens to the motion of the elevator? 90) A person is lowering a bucket into a well with a constant speed. How does the force exerted by the rope on the bucket compare to the bucket’s weight? 91) You ride on an elevator that is moving downward with constant speed while standing on a bathroom scale. The reading on the scale is __________ than your true weight, mg 92) A block of mass=55kg slides down a frictionless plane inclined at an angle 17° with the horizontal. The normal force exerted by the plane on the block is? 93) An object rests on an inclined surface. If the inclination of the surface is made steeper, what does the normal force on the object do? 94) Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest. It takes the heavier object _____times longer/shorter to reach the bottom of the incline than the lighter. 95) In a particle accelerator, a proton reaches an acceleration of 9.0 × 1013 m/s2. The mass of a proton is 1.7 × 10-27kg. What is the net force on the proton? 96) A flatbed truck is carrying a load of timber which is not tied down. The mass of the timber is 899 kg. The maximum static frictional force between the truck bed and the load is 5488 N. What is the highest acceleration that the truck can have without losing its load? What is the static coefficient of friction between the load and truck bed? 97) A hockey pucks collides head-on with a stationary puck on frictionless ice. The contact force between the two pucks is 37N, the acceleration of the originally stationary puck during the collision is 43.5m/s2. What is the mass of a hockey puck? 98) A 777 aircraft has a mass of 301,000 kg. At a certain instant during its landing, its speed is 27.0 m/s. If the braking force is -445,000 N, what is the speed of the airplane 10.0 s later (ignore air resistance)? 99) A catcher stops a ball traveling at 35. m/s in a distance of 20. cm and feels a force of 500. N against his glove. What is the mass of the ball? 100) A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the 3.0-kg box pushing it against the 5.0-kg box, and, as a result, both boxes slide along the floor. How large is the contact force between the two boxes? 101) 3.0-kg, 5.0-kg and 8.0kg boxes rest side-by-side in that order on a frictionless, level floor. A horizontal force of 32 N is applied to the 8.0-kg box, as a result, the three boxes slide along the floor. How large is the contact force between the 5.0kg and 8.0kg boxes? 102) A 1250kg boat is pulling a 72-kg water skier on a calm lake. Friction is negligible. The boat accelerates with an acceleration of 1.3 m/s2. What is the force exerted by the skier by the tow rope? 103) A locomotive is accelerating three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 78,000 kg, the next one, 51,000 kg, and the last one, 71,000 kg. Neglect friction. What is the force between the 50,000-kg and 70,000-kg wagons? 104) A 50.0-kg crate is being pulled along a horizontal frictionless surface. The pulling force is 10.0 N and is directed 20.0° above the horizontal. What is the acceleration of the crate? What is the normal force exerted on the crate by the ground? 105) A 40.0-kg box is being pushed along a horizontal frictionless surface. The pushing force is 15.0 N directed at an angle of 15.0° below the horizontal. What is the acceleration of the crate? What is the normal force exerted on the crate by the ground? 106) A person has a mass of 45 kg. How much does she weigh? How much less does she weigh on the Moon, where g = 1.62 m/s2? 107) A 16.2kg box is on a plane inclined at 44° above the horizontal. If the static coefficient of friction is 0.37 does the box accelerate down the ramp? If so, what is its acceleration? 108) A 40.0-kg crate is being lowered by means of a rope. Its downward acceleration is 2.00 m/s2. What is the force exerted by the rope on the crate? 109) A 36.0-kg child steps on a scale in an elevator. The scale reads 400. N. What is the direction and magnitude of the acceleration of the elevator? 110) A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0° on either side of the vertical direction. What is the tension in each cable? 111) A 10.0-kg picture is held in place by two wires, one hanging at 50.0° to the left of the vertical and the other is horizontal. What is the tension in the wires? 112) A 40.0-kg suitcase is being pulled along the ground by means of a strap which exerts a force of 10.0 N at an angle of 43.0° above the horizontal. What is the normal force exerted by the ground? 113) A block of mass m hangs from a string attached to a ceiling, as shown in Figure 5-16. An identical string hangs down from the bottom of the block. Which string breaks if (a) the lower string is pulled with a slowly increasing force or (b) the lower string is jerked rapidly downward? Explain. Figure 5-16 114) Is it possible for an object to be in motion and yet have zero net force acting on it? Explain. 115) A 7.50 N force pushes three boxes with masses m1=1.30 kg, m2=3.20 kg, and m3=4.90 kg, as shown in Figure 5-22. Find the magnitude of the contact force (a) between boxes 1 and 2, and (b) between boxes 2 and 3. Figure 5-22 116) A skier speeds down a trail, Figure 5-27. The surface is frictionless and inclined at an angle of 22.0° with the horizontal. (a) Find the acceleration of the skier. (b) Describe how the net force on the skier changes as the slope becomes steeper, shallower? Explain. Figure 5-27 117) As part of a physics experiment, you stand on a bathroom scale in an elevator. Your normal weight is 610 N, the scale at the moment reads 730 N. (a) Is the acceleration of the elevator upward, downward, or zero? Explain. (b) Calculate the magnitude of the elevator’s acceleration. (c) What, if anything, can you say about the velocity of the elevator? Explain. 118) A 2500kg car accelerates without any slippage, what type of friction is acting between the tires and the road? If the car accelerates from 0 to 21m/s in 5.2s what is the friction force with the road, neglect air resistance? Figure 6-1 119) In Figure 6-1, the block of mass 43.6kg is at rest on an inclined plane that makes an angle 25.1° with the horizontal. What is the force of static friction? What is the static coefficient of friction? Figure 6-2 120) In Figure 6-2 the scale at left is attached to the ceiling and a mass of 1.00 kg hangs from it. It reads 9.81 N. The identical scale at the right is connected by perfect strings passing over perfect pulleys to two 1.00 kg masses hanging vertically at the end of the strings. The scale at right reads _________ 121) An 82kg object experiences a wind force parallel to the surface of 600N. If µ s = 0.81 will the object slide? 122) When a baseball players slides into second base, the direction of the net force is? 123) Bobby (61kg) and Wayne (98kg) get in a tussle on the ice in a hockey game. If Bobby pushes Wayne with a force of 77N what is the acceleration of each backwards. Neglect friction. 124) Kyle is sledding with some friends at Snoqualmie pass and has never sledded before. They have two toboggans 6 ft long and 10ft long, but otherwise they are identical. Kyle chooses the longer one for his first trip so it won’t go so fast. Will Kyle’s idea work? Explain 125) A tired mom puts a 0.200-kg latte on the roof of her car and forgets it. The coefficient of static friction between the cup and the roof is 0.400. What is the maximum acceleration that the car can have if the cup is to stay in place? 126) A flatbed truck is carrying a 20.0-kg crate up a sloping road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place? 127) A policeman investigating an accident measures the skid marks left by a car at 28.0 m. He determines that the coefficient of kinetic friction between the tires and the road under the prevailing conditions was 0.300. How fast was the car going when the driver applied the brakes? (This car did not have anti-lock brakes.) 128) Had the car in question #127 had antilock brakes and kept the friction in static mode with a static coefficient of 0.420, what would the stopping distance be? 129) A 50.0-kg box is being pushed along a horizontal surface. The coefficient of kinetic friction between the box and the ground is 0.350. What horizontal force must be exerted on the box for it to accelerate at 1.20 m/s2? 130) A baseball player is running to 2nd base at 5.03 m/s. When he is 4.80 m from the plate he goes into a slide. The µk between the player and the ground is 0.180. What is his speed when he reaches 2nd base? 131) A 50.0-kg box is being pulled along a horizontal surface by means of a rope that exerts a force of 250 N at an angle of 32.0° above the horizontal. The coefficient of kinetic friction between the box and the surface is 0.350. What is the acceleration of the box? 132) A 50.0-kg box is being pushed along a horizontal surface by a force of 250 N directed 28.0° below the horizontal. The coefficient of kinetic friction between the box and the surface is 0.300. What is the acceleration of the box? 133) A 50.0-kg block is being pulled up a 13.0° slope by a force of 250 N which is parallel to the slope, but the block does not slide up the slope. What is the minimum value of µs required for this to happen? 134) A horse pulls a 555kg sleigh across a level snow covered field at constant speed. The µk= 0.15 between the sleigh and the snow. What is for force exerted on the horse by the sleigh? 135) A tightrope walker with a mass of 60.0 kg stands at the center of a rope which was initially strung horizontally between two poles. His weight causes the rope to sag symmetrically, making an angle of 4.80° with the horizontal. What is the tension in the rope? M1 M2 Figure 6.10 136) A 3.00-kg mass (M1) and a 5.00-kg mass (M2) hang vertically at the ends of a rope that goes over an ideal pulley (Figure 6.10). If the masses are released, what is the resulting acceleration of the system? 137) A 3.00-kg mass (M1) and a 5.00-kg mass (M2) hang vertically at the ends of a rope that goes over an ideal pulley (Figure 6.10). What is the tension in the string once the system is released? 138) Refer to Figure 6.10. If M1= 2.54kg and the system accelerates so M1 goes up at a rate of 3.96m/s2, what is the mass of M2? Figure 6-11 139) Refer to Figure 6-11. Block A has a mass of 3.00 kg and rests on a frictionless table and is connected to block B, which has a mass of 2.00 kg, after passing over an ideal pulley, as shown. Block B is released from rest. What is the acceleration of the system? 140) Refer to Figure 6-11. Block A has a mass of 4.66 kg and rests on a frictionless table and is connected to block B, which has a mass of 2.99 kg, after passing over an ideal pulley, as shown. Block B is released from rest. How long does it take block B to travel 80.0 cm? 141) Refer to Figure 6-11. Block A has a mass of 4.66 kg and rests on a table where µs = .452 between block A and the table. Block B, which has a mass of 2.99 kg, hangs vertically after passing over an ideal pulley, as shown. Block B is released from rest. What is the acceleration of the system? 142) Refer to Figure 6-11. Block A has a mass of 2.66 kg and rests on a table with friction. Block B, which has a mass of 1.99 kg, hangs vertically after passing over an ideal pulley, as shown. Block B is released from rest. If the system does not move, what is the static coefficient of friction between Block A and the table? Figure 6-12 143) Two masses are connected by a string which goes over an ideal pulley as shown in Figure 6-12. Block A has a mass of 3.0 kg and can slide along a frictionless plane inclined 30° to the horizontal. What is the mass of block B if the system is in equilibrium? 144) Two masses are connected by a string which goes over an ideal pulley as shown in Figure 6-12. Block A has a mass of 3.00 kg and can slide along a smooth plane inclined 30.0° to the horizontal. Block B has a mass of 2.00 kg. What is the acceleration of mass B? 145) Two masses are connected by a string which goes over an ideal pulley as shown in Figure 6-12. Block A has a mass of 3.00 kg and can slide along a frictionless plane inclined 30.0° to the horizontal. Block B has a mass of 0.500 kg. What is the acceleration of Block A? What is the tension in the string during the motion? 146) When you push a 1.80-kg book resting on a tabletop, it takes 2.25 N to start the book sliding. Once it is sliding, however, it takes only 1.50 N to keep the book moving with constant speed. What are the coefficients of static and kinetic friction between the book and the tabletop? 147) To move a large crate across a rough floor, you push on it with a force F at an angle of 21° below the horizontal, as shown in Figure 6-21. Find the force necessary to start the crate moving, given that the mass of the crate is 32 kg and the coefficient of static friction between the crate and the floor is 0.57. Figure 6-21 148) Pulling up on a rope, you lift a 4.25-kg bucket of water from a well with an acceleration of 1.80 m/s2. What is the tension in the rope? Figure 6-22 149) Three blocks connected by massless strings are being pulled along a horizontal frictionless surface by a horizontal force of 51N. If each block has mass = 5.4kg, what is the tension in the string connecting blocks B and C? 150) Below is data for three 6-dot intervals of ticker tape. The acceleration of 2 the object that created the below data is: _________m/s Time Position from from 0 t=0 0.10sec 0.15 m 0.20sec 0.45 m 0.30sec 0.90 m

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