Multiple ChoiceYou pull a 5kg box vertically up with a constant 100N force for 2m. How much work do you do?1698views24rank3comments
Multiple ChoiceYou push a 3kg box against a wall for a distance of 2m with a force of 40N that makes a 53° angle with the horizontal, as shown. Calculate the work done by gravity.1305views14rank4comments
Multiple ChoiceA 1000kg pallet of bricks is being lowered to the ground by a crane. If the bricks are moving at a constant speed, how much work is done by the cable on the bricks as they descend 11m?253views
Multiple ChoiceA particle of mass 250g moving along the x axis has velocity vx=(7.6x3)m/s with x measured in m. How much work is done on the particle as it moves from x=0.0m to x=2.0m?252views
Textbook QuestionA factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and the floor is 0.25. (e) What is the total work done on the crate?540views
Textbook QuestionTwo tugboats pull a disabled supertanker. Each tug exerts a constant force of 1.80×106N, one 14° west of north and the other 14° east of north, as they pull the tanker 0.75 km toward the north. What is the total work they do on the supertanker?1072views
Textbook QuestionA factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and the floor is 0.25. (d) How much work is done on the crate by the normal force? By gravity?1613views1rank
Textbook QuestionA factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and the floor is 0.25.(b) How much work is done on the crate by this force?1417views1rank
Textbook QuestionA factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and the floor is 0.25. (a) What magnitude of force must the worker apply?2646views1rank
Textbook QuestionA factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on it. The coefficient of kinetic friction between the crate and the floor is 0.25. (c) How much work is done on the crate by friction?468views
Textbook Question(I) A 55.0-kg firefighter climbs a flight of stairs 28.0 m high at constant speed. How much work does she do?137views
Textbook Question(II) Estimate the work you do to mow a lawn 10 m by 20 m with a 50-cm-wide mower. Assume you push with a horizontal force of about 15 N.117views
Textbook QuestionA 25 kg air compressor is dragged up a rough incline from r₁ (→ above r)= (1.3î + 1.3ĵ) m to r₂ (→ above r) = (8.3î + 2.9ĵ) m, to where the y-axis is vertical. How much work does gravity do on the compressor during this displacement?409views
Textbook QuestionThe energy used to pump liquids and gases through pipes is a significant fraction of the total energy consumption in the United States. Consider a small volume V of a liquid that has density p. Assume that the fluid is nonviscous so that friction with the pipe walls can be neglected. (a) An upward-pushing force from a pump lifts this volume of fluid a height h at constant speed. How much work does the pump do?360views
Textbook QuestionA 1000 kg elevator accelerates upward at 1.0 m/s² for 10 m, starting from rest. (b) How much work does the tension in the elevator cable do on the elevator?351views
Textbook QuestionThe three ropes shown in the bird's-eye view of FIGURE EX9.18 are used to drag a crate 3.0 m across the floor. How much work is done by each of the three forces?507views
Textbook QuestionObjects that rotate in air or water experience a torque due to drag. With quadratic drag, a drag torque that's negligible at low rpm quickly becomes significant as the rpm increases. Consider a square bar with cross section a x a and length L. It is rotating on an axle through its center at angular velocity ω in a fluid of density p. Assume that the drag coefficient C𝒹 is constant along the length of the bar. Find an expression for the magnitude of the drag torque on the bar. Hint: Begin by considering the drag force on a small piece of the bar of length dr at distance r from the axle.341views
Textbook QuestionConsider a force F(𝓍) = A𝓍³⸍² acting on an object moving in a straight line. Assume that A = 10.0 N/mᶻ. (b) Calculate the work done by this force as the object moves from 𝓍 = 0 to 𝓍 = 3.0m106views
Textbook Question(II) In a certain library the first shelf is 15.0 cm off the ground, and the remaining four shelves are each spaced 38.0 cm above the previous one. If the average book has a mass of 1.25 kg with a height of 22.0 cm, and an average shelf holds 28 books (standing vertically), how much work is required to fill all the shelves, assuming the books are all laying flat on the floor to start?142views
Textbook Question(II) A lever such as that shown in Fig. 7–20 can be used to lift objects we might not otherwise be able to lift. Show that the ratio of output force, F_O, to input force, F_I , is related to the lengths ℓ_I and ℓ_O from the pivot by F_O / F_I = ℓ_I / ℓ_O . Ignore friction and the mass of the lever, and assume the work output equals the work input.<IMAGE>106views
Textbook Question(I) The head of a hammer with a mass of 1.2 kg is allowed to fall onto a nail from a height of 0.65 m. What is the maximum amount of work it could do on the nail? Why do people not just “let it fall” but add their own force to the hammer as it falls?105views
Textbook Question(III) A 2800-kg space vehicle, initially at rest, falls vertically from a height of 2900 km above the Earth’s surface. Determine how much work is done by the force of gravity in bringing the vehicle to the Earth’s surface.112views
Textbook QuestionA package of mass m is placed onto a horizontal conveyor belt moving at speed v (Fig. 7–32). The coefficient of kinetic friction between package and belt is μₖ . <IMAGE>(d) How much of this work is done against friction and how much to accelerate the package?116views
Textbook QuestionA softball having a mass of 0.25 kg is pitched horizontally at 120 km/h. By the time it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the distance between the plate and the pitcher is about 15 m.130views
Textbook Question(II) A constant force F→ = (2.0 î + 4.0 ĵ) N acts on an object as it moves along a straight-line path. If the object’s displacement is d→ = (1.0 î + 5.0 ĵ) m, calculate the work done by using these alternate ways of writing the dot product:(a) W = Fd cosθ ; (b) W = Fₓdₓ + Fᵧdᵧ .112views
Textbook Question(II) A child is pulling a wagon down the sidewalk. For 5.0 m the wagon stays on the sidewalk and the child pulls with a horizontal force of 22 N. Then one wheel of the wagon goes off onto the grass so the child has to pull with a horizontal force of 38 N at an angle of 12° to the side for the next 3.0 m. Finally the wagon gets back on the sidewalk so the child makes the rest of the trip, 8.5 m, with a force of 22 N. How much total work did the child do on the wagon?101views
Textbook QuestionAn airplane pilot fell 370 m after jumping from an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only minor injuries. Assuming the pilot’s mass was 82 kg and his terminal velocity was 45 m/s, estimate: (c) the work done on him by air resistance as he fell. Model him as a particle.122views
Textbook Question(II) Consider a force F₁ = A /√x which acts on an object during its journey along the x axis from x = 0.0 to x = 1.0m, where A = 3.0 N • m¹⸍² . Show that during this journey, even though F₁ is infinite at x = 0.0, the work W done on the object by this force is finite, and determine W.106views
Textbook Question(III) A 3.0-m-long steel chain is stretched out along the top level of a horizontal scaffold at a construction site, in such a way that 2.0 m of the chain remains on the top level and 1.0 m hangs vertically, Fig. 7–27. At this point, the force on the hanging segment is sufficient to pull the entire chain over the edge. Once the chain is moving, the kinetic friction is so small that it can be neglected. How much work is performed on the chain by the force of gravity as the chain falls from the point where 2.0 m remains on the scaffold to the point where the entire chain has left the scaffold? (Assume that the chain has a linear weight density of 24 N/m.) <IMAGE>99views
Textbook QuestionTwo forces, F₁→ = (1.50î - 0.80 ĵ + 0.70k̂) N and F₂→ = ( - 0.70î + 1.20 ĵ) N, are applied on a moving object of mass 0.20 kg. The displacement vector of the object while the two forces act is d→ = (6.0 î + 8.0 ĵ + 5.0 k̂ ) m . What is the work done by the two forces?103views