Coal is burned to get energy. By burning coal, green houses gases like carbon dioxide, nitrogen oxides and suphur oxides are produced.
Rest of the energy sources given in the option are clean energies.
Answer is A.
The gravitational potential energy of the object is 100 J.
Gravitational potential energy stored in an object is the work done in raising the object to a height <em>h</em> against the gravitational force acting on it.
The gravitational force acting on a body is its weight mg, where m is its mass and g, the acceleration due to gravity.
Work done by a force is equal to the product of the force and the displacement made by the point of application of the force.

The weight of the object is given as 20 J and it is raised to a height of 5 m.

The gravitational potential energy of the object is 100 J.
Answer:
When an electric field exists in a conductor a current will flow.
This implies a voltage difference between two points on the conductor.
Electrostatics pertains to static charge distributions.
That means that an object such as a charged spherical conductor will be at the same potential (voltage) on both its outer and inner surfaces.
Answer:
T'=92.70°C
Explanation:
To find the temperature of the gas you use the equation for ideal gases:

V: volume = 3000cm^3 = 3L
P: pressure = 1250mmHg; 1 mmHg = 0.001315 atm
n: number of moles
R: ideal gas constant = 0.082 atm.L/mol.K
T: temperature = 27°C = 300.15K
For the given values you firs calculate the number n of moles:
![n=\frac{PV}{RT}=\frac{(1520[0.001315atm])(3L)}{(0.082\frac{atm.L}{mol.K})(300.15K)}=0.200moles](https://tex.z-dn.net/?f=n%3D%5Cfrac%7BPV%7D%7BRT%7D%3D%5Cfrac%7B%281520%5B0.001315atm%5D%29%283L%29%7D%7B%280.082%5Cfrac%7Batm.L%7D%7Bmol.K%7D%29%28300.15K%29%7D%3D0.200moles)
this values of moles must conserve when the other parameter change. Hence, you have V'=2L and P'=3atm. The new temperature is given by:

hence, T'=92.70°C
Answer:
15.07 ksi
Explanation:
Given that:
Pitch (P) = 5 teeth/in
Pressure angle (
) = 20°
Pinion speed (
) = 2000 rev/min
Power (H) = 30 hp
Teeth on gear (
) = 50
Teeth on pinion (
) = 20
Face width (F) = 1 in
Let us first determine the diameter (d) of the pinion.
Diameter (d) =
=
= 4 in
From the values of Lewis Form Factor Y for (
) = 20 ; at 20°
Y = 0.321
To find the velocity (V); we use the formula:


V = 2094.40 ft/min
For cut or milled profile; the velocity factor
can be determined as follows:


= 2.0472
However, there is need to get the value of the tangential load
, in order to achieve that, we have the following expression




Finally, the bending stress is calculated via the formula:



15.07 ksi
∴ The estimate of the bending stress = 15.07 ksi