Question

the mass & weight of an object on a earth & a mars are different give reasons

Answer 1

mass on every planet remains same but weight of body changes due to change in gravity of the planet.

Answer 2

Because mass is the amount of matter present in the object.It's value does not change . Hence mass of the object is same both on earth and mars.
Now, W=mg ....(where g is acceleration due to gravity )
The value of g depends on mass n radius of the planet/star.
The mass of the mars is 1/10th mass of the earth and radius of the mars is nearly half of the radius of the earth.
Therefore,weight of object on the mars is different from that on earth