Newton s 3 rd law .?

It states that every reaction has an equal and opposite reaction so how does a leaf falling from a certain height obey this law ?

1 Answer
Jun 30, 2017

See explanation

Explanation:

The way you stated the law is quite common but very misleading. In actual fact, it means that if object A provides a force onto object B, object B will provide:

  • An equal type of force
  • A force of equal magnitude
  • A force in the opposite direction
  • A force at the same time
  • A force onto object A

Using this, you can say that the Earth has a gravitational force of magnitude 9.81*m_l, where m_l is the mass of the leaf, pulling the leaf down.

At the same time, the leaf has a gravitational force of magnitude 9.81*m_l, however this is not noticeable as the acceleration due to gravity of the leaf onto the Earth is (9.81*m_l)/m_E where m_E is the mass of the Earth, as m_E is extremely large,and m_l extremely small, the value is very, very small. The gravitational force of the leaf onto the Earth pulls it upwards.

Also, the leaf provides a normal contact force downwards onto the air below with a magnitude of F_(atol), at the same time the air pushes up onto the leaf with a normal contact force with the same magnotude.