Crédits:
22 août 2013
This is a demonstration of the independence of the horizontal and vertical components of the velocity of a projectile. Often referred to as "the monkey and hunter," the problem is the following. Suppose a hunter (at ground level) points a gun directly at a monkey hanging from a branch high in a tree. The monkey, being very intelligent, does not want to be shot. It knows that light travels faster than bullets and reasons that, if it lets go of the branch the instant it sees the gun being fired, it will fall down far enough before the bullet reaches its destination and thus miss its mark. What happens? Unhappily the monkey does not know that the gravitational acceleration is the same for all falling objects (whether they be bullets or monkeys) and thus the bullet falls the same distance as the monkey, hitting it on the way down. Neither the bullet's initial velocity nor the distance between hunter and monkey is relevant to the final outcome, and affects only the height above the ground where bullet meets monkey.
In this video we see the spring-powered gun shooting the same steel ball bearing with two different initial velocities in an attempt to show that the initial speed of the ball does not matter. The shots at0:51, 1:00, and 1:09 are close to the maximum speed (roughly 13 m/s), while the shots at 1:18, 1:27, and 1:34 are close to the minimum (roughly 9 m/s). All other parameters remain the same for all trials; the horizontal distance is about 6.9 meters, and the launch angle is about 23 degrees above the horizontal.
For more details on our setup and for further references see:
http://sciencedemonstrations.fas.harv...