Answer:
the work converted to thermal energy is 40 J.
Explanation:
Given;
work done by the physicist,w = 100 J
height through which the book is raised, h = 0.2 m
efficiency of machine = 60% = 0.6
The useful work done by the machine is calculated as;
useful work = 0.6 x 100 = 60 J
The wasted energy = 100 J - 60 J
The wasted energy = 40 J
The wasted energy by the machine is possibly converted to thermal energy by the frictional part of the machine.
Therefore, the work converted to thermal energy is 40 J.
That would be like dropping your cell phone on to the ground by accident. The object (cell phone)'s gravitational potential energy would be converted to kinetic energy or energy in motion more precisely. This is just a hypothetical example though.
Usually to preserve the organisms (maybe the organisms are endangered species or need to be protected in some other way). Another reason could be for the benefit of mankind (for example, an artificial river provides recreational purposes)
Answer:
KE = 2.03 J
Explanation:
After impact, the kinetic energy of the bullet+block will convert to potential energy
½mv² = mgh
v = √(2gh) = √(2(9.81)(0.00500) = 0.0981 m/s
conservation of momentum during the collision
0.015u + 2.50(0) = (2.50 + 0.015)(0.0981)
u = 16.4481 m/s
KE = ½mv² = ½(0.015)16.4481² = 2.0290499...
KE = 2.03 J
