Question: A 100-kg box is placed on a ramp. As one end of the ramp is raised, the box begins to move downward just as the angle of inclination reaches 15°. What is the coefficient of static friction between box and ramp?
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Answer: 0.27
Question: Doug hits a hockey puck, giving it an initial velocity of 6.0 m/s. If the coefficient of kinetic friction between ice and puck is 0.050, how far will the puck slide before stopping?
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Answer: 37 m
Question: Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another. The cubes are lined up from left to right and a force is applied to the left side of the left cube causing all three cubes to accelerate to the right at 2.0 m/s². What is the magnitude of the force exerted on the right cube by the middle cube in this case?
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Answer: 12 N
Question: A sled weighs 100 N. It is held in place on a frictionless 20° slope by a rope attached to a stake at the top; the rope is parallel to the slope. Find the tension in the rope.
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Answer: 34 N
Question: A sled weighs 100 N. It is held in place on a frictionless 20° 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?
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Answer: 94 N
Question: 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?
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Answer: 250 N
Question: A 120 Newton box is at rest on an incline of 35 degrees. The surface of the incline is frictionless and a rope is attached to the box and exerts a force on the box that is 10 degrees above the incline. What is the force exerted by the rope on the box?
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Answer: 69.9 N
Question: 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/s², what is the tension in the connecting string between the blocks?
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Answer: 10 N
Question: Two blocks of masses 20 kg and 8.0 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8-kg mass is a second light string, which a person uses to pull both blocks horizontally. If the two-block system accelerates at 0.5 m/s², what is the tension in the second string attached to the 8-kg mass?
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Answer: 14 N
Question: 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 3.00 m/s²?
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Answer: 26 100 N
Question: Find the tension in an elevator cable if the 1 000-kg elevator is descending with an acceleration of 1.8 m/s², downward.
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Answer: 8 000 N
Question: Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another. The cubes are lined up from left to right and a force is applied to the left side of the left cube causing all three cubes to accelerate to the right at 2.0 m/s². What is the magnitude of the force exerted on the middle cube by the left cube in this case?
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Answer: 24 N
Question: A horizontal force of 200 N is applied to a 55-kg cart across a 10-m level surface. If the cart accelerates at 2.0 m/s², then what is the work done by the force of friction as it acts to retard the motion of the cart?
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Answer: -900 J
Question: A golf ball hits a wall and bounces back at 3/4 the original speed. What part of the original kinetic energy of the ball did it lose in the collision?
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Answer: 7/16
Question: A 1 200-kg automobile moving at 25 m/s has the brakes applied with a deceleration of 8.0 m/s². How far does the car travel before it stops?
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Answer: 39 m
Question: A 10.0-kg box starts at rest and slides 3.5 m down a ramp inclined at an angle of 10° with the horizontal. If there is no friction between the ramp surface and crate, what is the velocity of the crate at the bottom of the ramp?
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Answer: 3.5 m/s
Question: A hill is 100 m long and makes an angle of 12° with the horizontal. As a 50-kg jogger runs up the hill, how much work does gravity do on the jogger?
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Answer: -10 000 J
Question: A 20-N crate starting at rest slides down a rough 5.0-m long ramp, inclined at 25° with the horizontal. 20 J of energy is lost to friction. What will be the speed of the crate at the bottom of the incline?
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Answer: 4.7 m/s
Question: A pile driver drives a post into the ground. The mass of the pile driver is 2 500 kg and it is dropped through a height of 8.0 m on each stroke. If the resisting force of the ground is 4.0 × 10⁶ N, how far is the post driven in on each stroke?
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Answer: 4.9 cm
Question: A girl and her bicycle have a total mass of 40.0 kg. At the top of the hill her speed is 5.0 m/s, and her speed doubles as she rides down the hill. The hill is 10.0 m high and 100 m long. How much kinetic energy and potential energy is lost to friction?
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Answer: 2 420 J
Question: I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost?
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Answer: 0.29 J
Question: A horizontal force is applied to a 4.0 kg box. The box starts from rest moves a horizontal distance of 8.0 meters and obtains a velocity of 6.0 m/s. The system is frictionless. What is the horizontal force?
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Answer: 9 N
Question: A 5.0 kg box slides up a 10 m long frictionless incline at an angle of 20 degrees with the horizontal pushed by a 40 Newton force parallel to the incline. What is the change in kinetic energy?
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Answer: 232 J
Question: A 20 kg box slides down a 12.0 m long frictionless incline at an angle of 30 degrees with the horizontal. A force of 50 N is applied to the box to try to pull it up the incline. The applied force makes an angle of 10 degrees to the incline and above the incline. What is the increase in the kinetic energy of the box?
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Answer: 585 J