Which of the following property of a proton can change while it moves freely in a magnetic field?(a) Mass (b) Speed (c) Charge (d) Momentum

The property of a proton that can change while it moves freely in a magnetic field is (d) Momentum.

Here's why:

(a) Mass: The mass of a proton does not change in a magnetic field. It is a fundamental property of matter.

(b) Speed: The speed of a proton can change in a magnetic field, but only if there is an associated electric field or if the magnetic field is changing with time. In a constant magnetic field, the speed of a proton remains constant.

(c) Charge: The charge of a proton does not change in a magnetic field. It is a fundamental property of particles.

(d) Momentum: The momentum of a proton can change in a magnetic field. This is because the magnetic field can exert a force on the proton, and force can change the momentum of an object. The direction of the proton's velocity changes, which means its momentum changes. However, the magnitude of the velocity (and therefore the magnitude of the momentum) remains constant.