Answer: D
Explanation:
Let us examine the given actions to see which ones generate heat and sound energy from mechanical energy.
A) Stretching a string.
The mechanical stretching creates tension in the string, which is released when the tension is removed. The generation of thermal or sound energy is minimal or negligible.
B) Squeezing a sponge ball
The sponge ball experiences compressive loading. This generates minimal or no heat and sound energy.
C) Throwing a ball upwards in the air
Air friction generates minimal or no heat at low velocities. At low velocities the pressure waves are too small to generate sound.
D) Striking a hammer on a nail.
A tremendous amount of force is applied over a small area to generate very high stresses that are in the plastic zone. A high amount of thermal energy is generated and the localized disturbance of the air generates audible sound.
This is the correct situation.
Answer:
physical science
earth science and life science
Answer:
a) The resistance of the calf between the electrodes is 
b) The average resistivity of this part of the leg is 
Explanation:
Hi
a) Using Ohm's law 
, solving for 
, we obtain 
b) The volume of the calf is like a cylinder, so 
, with 
and 
, therefore 
. Then we can use 
, this is the average resistivity of this part of the leg.
Answer:
Why do we need to decrease friction? Friction is a necessary evil which causes a lot of wear and tear in machine parts that move against each other. It erodes the surfaces and destroys their symmetries. Hence, in such cases it is desirable to reduce friction.
Explanation:
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Answer:
applied force since she is pushing the box
maybe, I'm not 100% sure
