Question

Will is a scientist. He’s designing a spacecraft that would allow people to land on Mars. Will’s mass on Earth is 75 kilograms. Will knows that the gravitational pull of Mars is less than the gravitational pull of Earth. When he lands on Mars, his mass will be (Less than, Equal to or More than) 75 kilograms. His weight on Mars will be (less than, Equal to, or more than) his weight on Earth.

Answer 1

Mass is the amount of substance present inside the body.

As per Einstein's relativity the mass of the body increases with the increase of the speed of the body.

Mathematically it is given as $m=\frac{m_{0} }{\sqrt{1-\frac{v^2}{c^2} } }$

where m is the mass of the body during motion and $m_{0}$ is the rest mass.

Here V is the velocity of the body and c is the speed of light.

But during non-relativistic situation i.e the velocity of the body is very very less as compared to the velocity of the light or equal to zero, the mass of the substance remains unchanged.

Hence mass of Will will be the same both in Mars and Earth i.e 75 kg

Again the weight of a body is mathematically given as -

                             weight= mass×acceleration due to gravity

                           i.e W= m×g

The value of g is less in Mars as compared to Earth.

Hence the weight of Will on Mars is less as compared to weight on the Earth.

Answer 2

Mass will remain unchanged, always.  His weight, which is the gravitational force acting on that mass will be less in this case.