Question

I am trying an experiment with Electromagnets and looking for help to calculate force required. Please note I am not asking about electromagnets though since that would be electrical question.

So the problem is simple as depicted in image below. Lets say an object of M1 mass is moving in one direction (left to right or green arrow). It passes through the Cylinder M2. Now that cylinder applies a pull force on M1 in order to stop it first and then reverse it's direction with exact same velocity V1.

My assumption is the force required to reverse direction of M1 would be twice of the momentum M1 has. Meaning it will take 2(V1*M1). I say this because to stop the M1 Cylinder will have to apply same force V1*M1. Then to pull it back it will be another force of V1*M1.

My question is, am I thinking this correct or am I way off in how this mechanism works?

Note: Please ignore things like friction, gravity, energy gain by cylinder etc. I am just trying to understand basic physics to validate a concept.

Answer 1

To stop and reverse the direction of a moving object with the same velocity, a force equivalent to twice its original momentum is theoretically needed, assuming an ideal scenario without external influences such as friction.

Step-by-step explanation:

The concept of momentum is key in understanding the force required to stop and reverse the direction of a moving object. When discussing a mass M1 moving with velocity V1, its momentum is given by the product of its mass and velocity, M1*V1. To stop this object, a net force needs to be applied over some time to reduce its momentum to zero; that's where the impulse comes into play, and the impulse is equal to the change in momentum.

To reverse the direction with the same speed, the total change in momentum would be double the original momentum (because it's been stopped and then accelerated in the opposite direction), which translates into twice the impulse required. Thus, to reverse an object's direction with the same velocity, you would theoretically need to apply a force equivalent to twice the momentum of the object, considering that the situation is ideal and ignores other factors like friction, energy transfer, and external forces.