1M40.42 Ballistic Pendulum

1M40.42 Ballistic Pendulum

Blow into the dart gun to shoot a dart into the wooden pendulum. Based on the height that the pendulum swings, one can calculate the energy in the system and the initial velocity of the dart. This can also be used as a lab. Commercial Beck’s ballistic pendulum apparatus also available.

First, the basic idea: a blow gun dart strikes a hanging mass, which swings outward in response. A rail rig records the distance of the swing. Now, the details. A wooden cube is rigged to swing freely like a pendulum bob. The cube has a nail sticking out of the center of its bottom face. The cube is positioned to swing a few inches above the surface of a table. Two meter sticks rest on the table. The meter sticks are set on their long edges with thin wooden blocks pressed between them, creating a pair of 'rails'. Orange-handled clamps fasten each end of this make-shift rail system. The meter stick rails are set so that the nail on the underside of the wooden cube swings freely along the gap between the rails. A light piece of aluminum rests on top of the rails and can freely slide along them. When the pendulum cube swings up high enough, the nail on the underside will push this light aluminum piece along the rail, marking the distance traveled by the pendulum's swing. Separately from this rig, a small hollow metal tube is fastened horizontally to a small table stand, and set so that one end of the tube is even with the zero mark on the meter stick rail. A blow dart, obviously blown through this tube, is sticking in the side face of the wooden cube. The piece of aluminum rests about half-way down the meter stick rails, presumably marking the edge of the pendulum's swing after the blow dart struck it.

Blowgun Ballistic Pendulum

1M40_42

Beck’s Apparatus

Location: Blowgun Ballistic Pendulum:B4-4; Beck’s Apparatus: B3-1