Work and Energy
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A man with a mass of 75 kg climbs a staircase with 15 steps in 10 s. Each step is 20 cm in height and 30 cm in length. Determine:
a) The work done by the weight of a man climbing the ladder;
b) The average power delivered by man.

A body moves in a straight trajectory, the graph of force versus displacement of the body is shown in the following figure


a) Between what points there is no force acting on the body, between which points does the force produce movement, and between which points does the force resist movement?
b) What is the work done by the force, between points 0 and 60 m?

A car with a mass of 3000 kg accelerates under the action of a constant force from an initial speed of 18 km/h to 72 k /h. Determine:
a) The initial and final kinetic energies of the car;
b) What is the work done by the force between the initial and final instants?
c) What is the force needed to accelerate the car on a 500 m route?

A 50 g bullet hits a target with a speed of 500 m/s and penetrates 25 cm without deviating from the initial trajectory until it stops. Determine the magnitude of the average frictional force that resists penetration.

To draw water from a well, it is used a pump with a power of 3675 W. The well depth is 30 m. Calculate the volume of water taken in 24 h. The density of water is 1000 kg/m3.

A weight of 10 N is lifted from the rest, by a force of 30 N to a height of 5 m. Determine:
a) The work done by the force applied to raise the weight to the height given;
b) The work done by the gravitational force;
c) The speed of the body while reaching the height given.

A block with a mass equal to 5 kg is released with a constant speed of 0.4 m/s and shocks with a spring of elastic constant 80 N/m, and the surface is frictionless. Determine the maximum compression of the spring.
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