when an apple falls towards the earth, the earth moves up to meet the apple. is this true ?if yes, why is the earth's motion not noticeable?

Yes

Explanation:

Newton's third law

For every action, there is an equal and opposite reaction.

SO if the apple is falling 9.8 m/s2 then the same force is pushing against it.

Hope this helps

i'm on my way to history not a mistory.

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.