Gravitational potential energy is caused when an object is resting above the ground. It is released when the object is falling, not by burning substances.
Answer:
The speed of ejection is 
Solution:
As per the question:
Magnetic field density, B = 0.4 T
Density of the material in the sunspot, 
Now,
To calculate the speed of ejection of the material, v:
The magnetic field energy density is given by:

This energy density equals the kinetic energy supplied by the field.
Thus


where
m = mass of the sunspot in
= 


Answer : The correct option is, (B) -5448 kJ/mol
Explanation :
First we have to calculate the heat required by water.

where,
q = heat required by water = ?
m = mass of water = 250 g
c = specific heat capacity of water = 
= initial temperature of water = 293.0 K
= final temperature of water = 371.2 K
Now put all the given values in the above formula, we get:


Now we have to calculate the enthalpy of combustion of octane.

where,
= enthalpy of combustion of octane = ?
q = heat released = -81719 J
n = moles of octane = 0.015 moles
Now put all the given values in the above formula, we get:


Therefore, the enthalpy of combustion of octane is -5448 kJ/mol.
Answer:
Two possible points
<em>x= 0.67 cm to the right of q1</em>
<em>x= 2 cm to the left of q1</em>
Explanation:
<u>Electrostatic Forces</u>
If two point charges q1 and q2 are at a distance d, there is an electrostatic force between them with magnitude

We need to place a charge q3 someplace between q1 and q2 so the net force on it is zero, thus the force from 1 to 3 (F13) equals to the force from 2 to 3 (F23). The charge q3 is assumed to be placed at a distance x to the right of q1, and (2 cm - x) to the left of q2. Let's compute both forces recalling that q1=1, q2=4q and q3=q.





Equating


Operating and simplifying

To solve for x, we must take square roots in boths sides of the equation. It's very important to recall the square root has two possible signs, because it will lead us to 2 possible answer to the problem.

Assuming the positive sign
:




Since x is positive, the charge q3 has zero net force between charges q1 and q2. Now, we set the square root as negative



The negative sign of x means q3 is located to the left of q1 (assumed in the origin).