Which force is responsible for the motion of the moon around earth?

The correct answer is Centripetal.

Key Points

• Centripetal force:
  • A force that acts on a body moving in a circular path and is directed towards the centre around which the body is moving.
  • This force is applied to the object from outside and for this reason, the centripetal force is an external force.
  • It acts always towards the center (so we do not assume that it is an internal force) but it is an external force.
  • Example: When we spin a ball on a string our hand always apply the centripetal force to the ball. So, the force applied by us is an external force on the ball.

Additional InformationVan der Waals

• The equation is basically a modified version of the Ideal Gas Law which states that gases consist of point masses that undergo perfectly elastic collisions. Ideal gas equation fails to explain the behaviour of real gases. Therefore, the Van der Waals equation was devised and it helps us define the physical state of a real gas.
• Van der Waals equation is an equation relating the relationship between the pressure, volume, temperature, and amount of real gases. For a real gas containing ‘n’ moles, the equation is written as

\(\left ( P+\frac{an^{2}}{V^{2}} \right )\left ( V-nb \right )=nRT\)

here, P = Pressure, V = Volume, T = Temperature, R = Gas constant, n = Number of moles

• Frictional
  • The opposing force which comes into play when a body moves or tries to move the surface of another body is known as friction.
  • The maximum value of the force of friction that comes into play before a body just begins to slide over the surface of another body is called limiting friction.

• Centrifugal force
  • It is equivalent and opposite to the centripetal force and it is the force produced as a result of the centripetal force.
  • ​​Centrifugal force is also known as pseudo force.
  • Cream separator works on the principle of centrifugal force.