Question

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 ?

Answer 1

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.