Physics Help Forum Office argument needs settling

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 May 11th 2009, 07:32 AM #1 Junior Member   Join Date: May 2009 Posts: 3 Office argument needs settling Good afternoon Bit of a silly one but needs sorting! I am currently having an argument with one of my colleagues at work and would appreciate it if someone could settle it!! Scenario: I'm stood at the top of the Eifel Tower, I have a golf ball in one hand and one in a cannon (pointing horizontally) I drop the golf ball by hand and simultaneously fire the cannon......which will hit the ground first?!....I am adamant that the 'cannon golf ball' will take longer to reach the ground. Please could someone solve this argument. Regards
 May 11th 2009, 10:09 AM #2 Physics Team   Join Date: Feb 2009 Location: India Posts: 365 In absence of air the two balls will take same time. I am not sure about what happens in presence of air.
 May 11th 2009, 07:58 PM #3 Senior Member   Join Date: Feb 2009 Location: Singapore Posts: 206 they should hit the ground at the same time
 May 12th 2009, 07:23 AM #4 Junior Member   Join Date: May 2009 Posts: 3 Thankyou for your replies
 May 12th 2009, 10:33 AM #5 Physics Team   Join Date: Feb 2009 Posts: 1,425 In the presence of air both balls will experience a drag / frictional force which is generally proprtional to the square of the velocity. Since the vertical motion of both the balls is identical and so are their surfaces, both will experience identical retarding forces, so both will take the same time. However the time taken will be larger than in the case without air, as the net acceleration is now < g. As far as the horizontal motion goes, it should cover the same distance i think because though the time taken is larger, the horz velocity also decreases and both depend on v^2. Vertically the resistive force increases with time and horizontally it decreases with time.
 May 13th 2009, 03:43 AM #6 Junior Member   Join Date: May 2009 Posts: 1 Golf Ball The golf ball fired out of the cannon ( with air present ) will take slightly longer due to the fact the it has to travel through more air and therefore the resistance will cause more lag than the ball dropped vertically. Hope that answers your question.
 May 13th 2009, 07:06 AM #7 Junior Member   Join Date: May 2009 Posts: 1 Who won the arguement then Congerball?
 May 13th 2009, 11:43 AM #8 Physics Team   Join Date: Feb 2009 Posts: 1,425 The golf ball fired out of the cannon ( with air present ) will take slightly longer due to the fact the it has to travel through more air and therefore the resistance will cause more lag than the ball dropped vertically. Hope that answers your question. Since the vertical displacement is the same, the time taken will be the same.
 May 14th 2009, 03:43 AM #9 Junior Member   Join Date: May 2009 Posts: 3 Once again thanks for the replies.....I won the argument!!
 May 14th 2009, 10:19 AM #10 Physics Team   Join Date: Feb 2009 Posts: 1,425 But maybe physics lost!

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