How does a rubber rod become negatively charged through friction?
a: it touches a negatively charged object, and protons move off of the rod.
b: it touches a positively charged object, and electrons move onto the rod.
c: it is rubbed with another object, and electrons move onto the rod.
d: it is rubbed with another object, and protons move off of the rod.

The correct answer to the question is C) It is rubbed with another object, and electrons move onto the rod.

EXPLANATION:

Before going to answer this question, first we have to understand the charging by friction.

Charging by friction is one mode of charging a body by rubbing it with another body in which there will be actual transfer of electrons from one body to another body.

In this process, the electrons will be transferred from a low affinity body to a high affinity body. The high electron affinity body will be negatively charged as it accepts electron, and the low electron affinity body will be positively charged.

As per the question, the charge of rubber rod is negative. Hence, it must have rubbed with another object, and electrons move onto the rod.

The protons can not move onto the rod as protons are bound to the nuclei of atoms.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.