Answer:
Force of static friction between the two surfaces
Explanation:
When two surfaces come into contact, they exert a force that resist the sliding of the two surfaces. This force is called static friction.
This force is given by the relation

Where,
μ - coefficient of static friction
η - normal force acting on the body
When a force acts on a body placed on a rough surface, it doesn't do any work if the applied force was less than the force of static friction.
So, in order to move the body, the applied force should be greater than the force of static friction.
<h2>Hello!</h2>
The answer is: D. Coal
<h2>
Why?</h2>
Coal power plants burn coal in to get steam, the steam flows into a turbine which is coupled to an electrical generator.
Coal power plants work burning high amounts of coal into a boiler, generation a lot of steam under extreme pressures. The steam is obtained when the water is heated by the burning coal, then the steam is cooled, being transformed in liquid water again (due the condensation process) and it's sent back on a cyclical process.
Have a nice day!
Answer:
x=0.154kg
Explanation:
(x*L)+(0.5kg*4200*50)+(x*4200*(-50)=0
(x*333 000J/kg*c)+(0.5kg*4200J/kg*C*(-40C))+(x*4200J/kg*C*50C)=0