Problem 12: When water flows through river rapids or over a waterfall, it experiences a decrease in height and thus a decrease in gravitational potential energy. Some of this energy goes into producing noise and eroding rock, but much of the energy goes into heating the water. A river flows over a waterfall of height h = 41 m. Assume all the available gravitational energy is converted into internal energy of the water. There is no change in the kinetic energy, because the flow speed of the river is the same above and below the waterfall. Part (a) Enter an expression for the change in temperature of the water, in terms of the height of the waterfall, h, the specific heat of water, c, and the acceleration due to gravity, g. Part (b) Calculate the change in temperature, in degrees Celsius, of the river water in this problem. The specific heat of water is 4.19×103 J/(kg⋅°C).
Kinematics
A machine is a device that accepts energy in some available form and utilizes it to do a type of work. Energy, work, or power has to be transferred from one mechanical part to another to run a machine. While the transfer of energy between two machine parts, those two parts experience a relative motion with each other. Studying such relative motions is termed kinematics.
Kinetic Energy and Work-Energy Theorem
In physics, work is the product of the net force in direction of the displacement and the magnitude of this displacement or it can also be defined as the energy transfer of an object when it is moved for a distance due to the forces acting on it in the direction of displacement and perpendicular to the displacement which is called the normal force. Energy is the capacity of any object doing work. The SI unit of work is joule and energy is Joule. This principle follows the second law of Newton's law of motion where the net force causes the acceleration of an object. The force of gravity which is downward force and the normal force acting on an object which is perpendicular to the object are equal in magnitude but opposite to the direction, so while determining the net force, these two components cancel out. The net force is the horizontal component of the force and in our explanation, we consider everything as frictionless surface since friction should also be calculated while called the work-energy component of the object. The two most basics of energy classification are potential energy and kinetic energy. There are various kinds of kinetic energy like chemical, mechanical, thermal, nuclear, electrical, radiant energy, and so on. The work is done when there is a change in energy and it mainly depends on the application of force and movement of the object. Let us say how much work is needed to lift a 5kg ball 5m high. Work is mathematically represented as Force ×Displacement. So it will be 5kg times the gravitational constant on earth and the distance moved by the object. Wnet=Fnet times Displacement.
Problem 12: When water flows through river rapids or over a waterfall, it experiences a decrease in height and thus a decrease in gravitational potential energy. Some of this energy goes into producing noise and eroding rock, but much of the energy goes into heating the water. A river flows over a waterfall of height h = 41 m. Assume all the available gravitational energy is converted into internal energy of the water. There is no change in the kinetic energy, because the flow speed of the river is the same above and below the waterfall.
Part (a) Enter an expression for the change in temperature of the water, in terms of the height of the waterfall, h, the specific heat of water, c, and the acceleration due to gravity, g.
Part (b) Calculate the change in temperature, in degrees Celsius, of the river water in this problem. The specific heat of water is 4.19×103 J/(kg⋅°C).
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