- Wait until Java finishes loading before clicking on anything. If you can't see buttons above,
switch your browser to fullscreen
- Initialize the demonstration problem by clicking on the "Initialize" button.
- Click "Shoot New Bullet." Click "Pause" to stop the bullet.
- The point of the problem is to hit the target. Notice that the target has a constant
speed of 25 m/s. What must be the launch speed of the bullet in order to hit the
target? Enter that speed in the corresponding box. You don't have to push
Enter. Now shoot the bullet. (Note that you always have to click "Pause"
to stop the bullet. If you wish, you can use the step frame buttons to position the bullet
- Assuming you were successful, change the gun altitude to, say, 150 m. How will this
affect the launch speed? Try it.
- Change the gravitational field to that on the Moon, 1.6 N/kg. How will this affect the
launch speed needed to hit the target?
- Initialize the problem again. What must the launch angle be in order to hit the
target? Try it. (It's OK if the projectile goes off screen. It should find its way
If you were successful, you either knew the physics already or you learned something
fundamental: The horizontal motion of the projectile is independent of the vertical
motion. For a horizontal launch angle, the launch speed needed to hit the target was
unaffected by gun altitude and gravitational field strength. For a different launch angle,
it was only necessary to change the magnitude of the launch velocity so that its horizontal
component remained unchanged.