A crate with a mass of 72.0 kg is pulled up an inclined surface by an attached rope, which is driven by a motor. The crate moves a distance of 45.0 m along the surface at a constant speed of 2.3 m/s. The surface is inclined at an angle of 30.0° with the horizontal. Assume friction is negligible. (a) How much work (in kJ) is required to pull the crate up the incline? kJ (b) What power (expressed in hp) must a motor have to perform this task? hp

A crate with a mass of 72.0 kg is pulled up an inclined surface by an attached rope, which is driven by a motor. The crate moves a distance of 45.0 m along the surface at a constant speed of 2.3 m/s. The surface is inclined at an angle of 30.0° with the horizontal. Assume friction is negligible. (a) How much work (in kJ) is required to pull the crate up the incline? kJ (b) What power (expressed in hp) must a motor have to perform this task? hp

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter7: Conservation Of Energy

Section: Chapter Questions

Problem 79P: A block of mass 0.500 kg is pushed against a horizontal spring of negligible mass until the spring...

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Cite two examples in which a force is exerted on an object without doing any work on the object.
A block of mass m = 2.50 kg is pushed a distance d = 2.20 m along a frictionless, horizontal table by a constant applied force of magnitude F = 16.0 N directed at an angle = 25.0 below the horizontal as shown in Figure P6.3. Determine the work done on the block by (a) the applied force, (b) the normal force exerted by the table, (c) the gravitational force, and (d) the net force on the block. Figure P6.3
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What is the dominant factor that affects the speed of an object that started from rest down a frictionless incline if the only work done on the object is from gravitational forces?
A block of mass 0.500 kg is pushed against a horizontal spring of negligible mass until the spring is compressed a distance x (Fig. P7.79). The force constant of the spring is 450 N/m. When it is released, the block travels along a frictionless, horizontal surface to point , the bottom of a vertical circular track of radius R = 1.00 m, and continues to move up the track. The blocks speed at the bottom of the track is = 12.0 m/s, and the block experiences an average friction force of 7.00 N while sliding up the track. (a) What is x? (b) If the block were to reach the top of the track, what would be its speed at that point? (c) Does the block actually reach the top of the track, or does it fall off before reaching the top?
Repeat the preceding problem, but this time, suppose that the work done by air resistance cannot be ignored. Let the work done by the air resistance when the skier goes from A to B along the given hilly path be —2000 J. The work done by air resistance is negative since the air resistance acts in the opposite direction to the displacement. Supposing the mass of the skier is 50 kg, what is the speed of the skier at point B ?
As shown in Figure P7.20, a green bead of mass 25 g slides along a straight wire. The length of the wire from point to point is 0.600 m, and point is 0.200 in higher than point . A constant friction force of magnitude 0.025 0 N acts on the bead. (a) If the bead is released from rest at point , what is its speed at point ? (b) A red bead of mass 25 g slides along a curved wire, subject to a friction force with the same constant magnitude as that on the green bead. If the green and red beads are released simultaneously from rest at point , which bead reaches point first? Explain. Figure P7.20