Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

When two balls of different masses, thrown from equal height they reaches the ground at the same time. Can anyone explain this in terms of laws of Physics(or with mathematical equations)?

share|improve this question

marked as duplicate by Waffle's Crazy Peanut, Brandon Enright, user1504, David Z Jun 11 '13 at 20:20

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
Too localized. Now, it turns out to be a possible duplicate –  Waffle's Crazy Peanut Jun 11 '13 at 18:04
    
Also of physics.stackexchange.com/questions/5973 (I thought it would show the second link when I closed it, but apparently not) –  David Z Jun 11 '13 at 20:21
add comment

2 Answers 2

up vote 0 down vote accepted

Newton's law says that the force $\vec F$ exercing on an object produces an acceleration $\vec a$ such as :

$$\vec F = m_I \vec a$$ where $m_i$ is the inertial mass of the object.

On the other side, in your experience, the force is the gravitationnal force (the weight) $\vec P$ which is

$\vec P = m_G \vec g$, where $m_G$ is the gravitational mass, and $\vec g$ is the gravity acceleration.

The equivalence principle says that the inertial mass and the gravitational mass are equal, so $m_G = m_I$.

You have $\vec F =\vec P$, that is $m_G \vec g = m_I \vec a$

But $m_G = m_I$, so the acceleration is $\vec a = \vec g$, and this does not depends on the mass.

share|improve this answer
add comment

This is because both experience the same acceleration, g(9.81 m/s2). The acceleration is independent of mass. Thus when they are dropped, they will always maintain the same velocity and travel the same distance (neglecting air resistance of course!) in the same time.

share|improve this answer
    
"neglecting air resistance of course!" and Archimedes' principle too ... some balls tend to float upward. –  babou Jun 11 '13 at 23:21
add comment

Not the answer you're looking for? Browse other questions tagged or ask your own question.