Newton's first law of motion is often stated as:
An object at rest stays at rest and an object in motion stays in motion with the
same speed and in the same direction unless acted upon by an unbalanced force.
Most people believe that if an object is moving upward and rightward, there must be both an upward and rightward force….
…but they are wrong!
In our experiment we will be investigate the forces acting on a moving golf ball:
By definition, a projectile is an object upon which the only force acting is gravity.
Our 'projectile' will be a golf ball (although, feel free to experiment with pianos and human cannonballs).
We are interested in forces acting AFTER the golf ball (projectile) has been thrown/launched.
Q2. CLICK HERE TO SEE / HIDE STUDENT FLIP RESOURCES:
Watch this video first - it will teach you how to use the 'Projectile motion interactive':
Video: Projectile motion introduction
Simulator/Interactives:
Play the video above… then try the simulator for yourself (requires Flash):
The Golf Interactive (below) provides an environment for learners to investigate that classic question:
Find your own links on the Internet - Make a note of any good resources so that you can share them in class. Add your links to the comments section.
Q2. CLICK HERE TO SEE / HIDE EXTRA STUDENT FLIP RESOURCES
Hint: A golf ball in flight is a type of 'projectile'.
Here are some other types of projectiles..
An object dropped from a hand (from rest) is a projectile.
An object that is thrown vertically upward is also a projectile.
An object which is thrown upward at an angle to the horizontal is also a projectile:
What forces are pushing or pulling on these objects after they have been hit, dropped or thrown?
If you think about what happens when someone hits a ball:
Does a 'hit' from a golf club affect the ball before the club touches the ball?
Does a 'hit' from a cricket bat affect the ball before the bat touches the ball?
Can a carpenter hammer a nail into timber before the hammer hits?
If you answered 'NO' to any of the above questions, then why do you think that the 'hit' has an effect AFTER the ball has been hit?
So long as the ball and the golf club are no longer touching, then the club no longer has any effect?
If you think about it, all that the 'hit' from the club does, is to put the ball into motion.
Once the ball has moved out of range, nothing you can do with the club will have any effect.
It is true that the club was one of the things that 'caused' the direction that the ball took when it was hit, but once something is moving, it will keep on moving in the same direction until something else stops or diverts it - no matter whether the thing(s) that caused the motion still exist or not.
So, as soon as the ball has moved away from the golf club, the ball will continue in a straight line forever… unless it is stopped or diverted by something else.
Which of the following do you think could affect the flight of the ball after it has been hit:
Wind and air pushing against the ball?
Birds or other flying objects hitting the ball and changing its course while it is in the air?
A solid object that is much bigger (more massive) than the ball - such as a tree, a house or a planet?
Gravity pulling the ball down towards the Earth?
Why not search for the word 'projectile' on the Internet and see what you find.
Can you think of an experiment that might confirm or disprove the above?
Do you have any ideas about what happens when you hit a ball?
Leave your comments below:
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THERE ARE MORE DISCOVERY ACTIVITIES FOR THIS QUESTION: ALSO SEE FUN WITH PROJECTILES
