Question

when a ball hits the ground, it exerts a force on the earth. according to newtons 3rd law, what is the response of the earth?
a the earth exerts no force on the ball.
b the earth exerts a force on the ball equal in size but opposite in direction.
c the earth exerts a greater force on the ball than the ball exerts on the earth.
d the force the earth exerts is dependent on the mass of the ball.

Explanation:

Newton's 3rd Law states that for every action, there is an equal and opposite reaction. When the ball exerts a force on the Earth (action), the Earth exerts a force on the ball (reaction) that is equal in magnitude and opposite in direction.

• Option A is incorrect because it violates Newton's 3rd Law which requires a reaction force.
• Option C is wrong as the forces are equal in magnitude according to the law.
• Option D is not in line with Newton's 3rd Law which emphasizes the equality and opposition of forces, not mass - dependence for the reaction - force magnitude in this context.

Answer:

B. The Earth exerts a force on the ball equal in size but opposite in direction.