Ballistic catcher lab | Mistake Master Studio

The situation

A soft catcher block hangs at rest from a rigid arm in front of a launcher. Fire a ball of mass m horizontally at speed v: it buries itself in the block, stays there, and the pair swings up together before falling back. A rise marker on the rail beside the catcher latches at the very top of the climb and reads the height of the latch above the rest position, in centimeters. Below you will get a working rig with three knobs: the launch speed v, the ball mass m, and the length of the arm the catcher hangs from.

First, commit to a prediction. Then the apparatus unlocks.

Predict first

Commit before you touch the sliders

Which changes make the rise marker latch higher? Check all you expect to. Firing the ball faster Firing a heavier ball at the same speed Hanging the catcher from a longer arm

Plot rise height versus launch speed. What shape do you expect? A straight line sloping up (each added meter per second buys the same extra rise) A curve that starts shallow and steepens as the speed grows (h is proportional to v²) A flat line (launch speed has no effect)

Explore

Test your prediction on the apparatus

Drag the sliders and latch the rise marker at different settings. Or pick a test chip to lock everything but one variable and watch its relationship with h draw itself. The v slider sets how fast the ball leaves the launcher; the m slider swaps in a lighter or heavier ball; the L slider hangs the catcher from a shorter or longer arm (the mount slides so the catcher always sits in front of the launcher). The catcher is labeled M = 0.200 kg, the ball buries itself in the soft face and stays, the pivot is frictionless, air resistance is negligible, and the rig sits on Earth, g = 10 N/kg. Re-latching at identical settings repeats exactly, so any change you see is real.

Launch speed vv = 4.00 m/s

Ball mass mm = 0.060 kg

Arm length LL = 0.80 m

Mystery catcher: M = ?

Rise height vs launch speed

Drag the unlocked slider. Every position you visit drops a measured point.

Which fit matches your points?

Measure and straighten

How heavy is the sealed catcher?

The catcher has been sealed and its mass is hidden. So the slope stays honest, the ball is fixed at m = 0.100 kg (stated on the launcher), the catch stays soft, the pivot stays frictionless, and g = 10 N/kg. Choose at least 5 different launch speeds, latch the rise marker at each, convert each reading to a height in meters (the marker reads centimeters: divide by 100), and enter each (v, h) pair below. Then straighten the plot, and work through Read the slope: the walkthrough hands you the catcher mass only once you can say why the slope carries it, and the catcher mass opens the seal.

Collect your data, then work through the Read the slope steps: they walk you to the transform that straightens the plot and the slope that carries the catcher mass M. Finish them and the Record button turns on and checks your M against the sealed catcher.

Transfer

One changed variable

Back on the open rig, a friend swaps the labeled 0.200 kg catcher for a 0.400 kg one and fires the same 0.100 kg ball at the same speed. Same ball, same speed, same kinetic energy arriving, they argue, so the pair should rise to the same height. What actually happens?

The catch decides, and the catch conserves momentum, not kinetic energy. The pair's mass grows from 0.300 kg to 0.500 kg, so V = mv / (m + M) drops to 3/5 of what it was, and the rise h = V² / (2g) drops to 9/25: about a third of the old height. The friend's argument breaks inside the soft catch: crushing the foam turns most of the arriving kinetic energy into heat, and only the fraction m / (m + M) survives to become climbing energy. The heavier the catcher, the smaller that surviving fraction. Notice the arm length never entered the reasoning, exactly as your slider showed.