World of Physics
Click here for summary of physics specific material up to (but not including) forces.
More simulations at St Mary's site. (Thanks to Tony Mangiacapre)
Topic: 2-dimensional motion
B-52 Bomber video Important to notice: The bombs continue to move with the same horizontal velocity as the plane. For motion in two dimensions, the vertical and horizontal components are independent of each other. As the bombs fall, (ignoring air resistance) they will continue to have the exact same horizontal velocity as they had at the moment they were released. The vertical velocity will increase at a rate of 9.81 meters per second squared. (Or, every second, the vertical velocity will increase by 9.81 meters per second.) In the "real world" air resistance can be signficant. For example, if you drop a heavy steel ball from the window of a moving car, it will appear to fall vertically (as viewed by someone sticking their head out the window looking down.) However, if a styrofoam coffee cup were dropped from a moving vehicle, it would appear to move backwards as viewed by the person looking out the window. In each case, an observer watching from the side of the road would see the object move forward. In the case of the heavy, solid ball, the ball would appear to stay in line with the point of the car at which it was dropped. In the case of the cup, it would move forward, but appear to slow down significantly compared to the velocity of the car. Why? Air resistance is a significant factor for the styrofoam cup.
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