You're the first person to visit mars and you've just met a group of martian schoolchildren. they are playing street hockey with parts from the mars polar lander and, after years of watching star trek reruns, they are fluent in english. one of them asks you how your weight and mass have changed since you left earth. you take a moment to measure both and reply correctly that

(a) your weight is essentially unchanged but your mass is less than on earth.
(b) your mass is essentially unchanged but your weight is less than on earth.
(c) your weight and mass have both changed significantly.
(d) neither your weight nor your mass have changed much.

(B) your mass is essentially unchanged but your weight is less than on Earth.

Explanation:

Well, firstly we have to explain the difference between the concepts of mass and weight:

-Mass is the amount of matter that exists in a body, which only depends on the quantity and type of particles within it. This means mass is an intrinsic property of each body and remains the same regardless of where the body is located.  

-Weight is a measure of the gravitational force acting on an object and is directly proportional to the product of the mass of the body by the acceleration due gravity in that place and is mathematically expressed as:  

So, according to this explanation and since the Earth and Mars have different values of acceleration due gravity (in fact, Mar's is less than Earth's), your weight has changed, but not your mass.

no. dot product   =0 when vecs at right angles

its c i just checked it