Question

Following Newton's Third Law, when a cannon goes off the cannon ball exerts a force on the cannon and the cannon exerts the same force back on the cannon ball. Why does the cannon ball travel severl hunder feet while the cannon itself only moves a few inches?

Question 5 options:

Because the mass of the cannon ball is much less than the cannon

Because the cannon is so much larger in size than the cannon ball

Because the cannon ball is more aerodynamic than the cannon

Because the forces were not really equal

Answer 1

• First choice: Because the mass of the cannon ball is much less than the cannon

Step-by-step explanation:

Indeed, Newton's Third Law, i.e. the action-reaction law, states that any action (force) will have a reaction (force) of same magnitude but opposite direction.

That means that when a cannon goes off the cannon ball exerts a force on the cannon and the cannon exerts the same force back on the cannon ball.

To find out how much the cannon ball and the cannon itsel move, you must consider Newton's second law.

• F = m×a (force equal mass times acceleration).

Clearing the acceleration you get:

• a = F / m

Then, since the mass is in the denominator and both the force that the cannon ball exerts on the cannon and the cannon exerts on the cannon ball are equal in magnitude, then the body that has the smaller mass (the cannon ball) will experience a greater acceleration, which is stated by the first choice: because the mass of the cannon ball is much less than the cannon.