I've been wondering about this punching machine that you can find at every fair. A ball is punched by alpha males to impress female public. This punch is then measured and a score is calculated. I've seen enough videos to be convinced that this machine doesn't just randomly give a score but indeed bases this number on the force that is used to punch the ball.

Of course, the obvious answer would be, measuring the speed of the lever to which this ball is attached. However, I am looking for something that can withstand the force of the ball and calculate the newtons that the ball received.

I've been googling for the correct sensors but I can't find the relevant specification. I always thought to be somewhat competent at googling but slowly I'm losing confidence.

Many thanks in advance for all the helpful answers!

Newton's second law of motion is, F = ma where F represents force, m represents mass and a represents acceleration.
If you know the mass of the ball and measure its acceleration then you can calculate the force of the punch.

Punching machines have different designs. If the the boxer is puching against a spring mounted pad then you could measure the displacement of the pad and calculate the force needed to compress the spring by that amount.

Perhaps you could have a ball mounted on a solid stick with a strain gauge and calculate the force from the strain.

You can make this project with a pair of break-beam sensors.

When ball is in its resting state one sensor is blocked, when the ball is moved to a fixed point the other sensor becomes blocked.
Using the time difference you can calculate approximate force.

Add couple more sensors in the path to give a wider range of “weak” impacts.