In Fig., a block of ice slides down a frictionless ramp at angle while an ice worker pulls on the block (via a rope) with a force that has a magnitude of and is directed up the ramp. As the block slides through distance along the ramp, its kinetic energy increases by . How much greater would its kinetic energy have been if the rope had not been attached to the block?
Kinetic Energywould begreater by ifthe rope had not been attached to the block.
From the figure, we can say thatthe block is moving inadownward direction. If the rope is attached, the kinetic energy will decrease by some amount. We have to find this kinetic energy.
We know that the work done can be calculated as,
Substitute the values in the above expression, and we get,
The negative sign says thatthe work done is along the opposite direction of motion of the block, which means the motion of the block and the pull from the rope are in opposite directions.
If there is no rope attached to the system, the block will move freely downward. Hence, kinetic energy will increase by as comparedto when a rope is attached to the system.
Figure 7 -42 shows a cold package of hot dogs sliding rightward across a frictionless floor through a distance while three forces act on the package. Two of them are horizontal and have the magnitudes and ; the third is angled down by and has the magnitude . (a) For the 20.0 cm displacement, what is the net work done on the package by the three applied forces, the gravitational force on the package, and the normal force on the package? (b) If the package has a mass of 2.0 Kg and an initial kinetic energy of 0, what is its speed at the end of the displacement?
To push a 25.0 kg crate up a frictionless incline, angled at to the horizontal, a worker exerts a force of 209 N parallel to the incline. As the crate slides1.50 m, how much work is done on the crate by (a) the worker’s applied force, (b) the gravitational force on the crate, and (c) the normal force exerted by the incline on the crate? (d) What is the total work done on the crate?
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