A spaceship continues moving in space with constant speed because of
A) no force of friction due to air acts on it.
B) no force of gravitational acts on it.
C) Its mass is zero in space.
D) None of these.

Hint: In the space there is no atmosphere in the space. The gravitational force on the spaceship will not be that effective as it used to be of the planet earth. There is no external force acting on the spaceship except the combustion of fuel.

Complete step by step answer:
As the spaceship is an environment where there is no atmosphere which means that the resistance caused due to the air or the dust particles in the air is neglected. The fuel burnt causes the spaceship to move in a particular direction but there is no resistance to the motion which ensures that the spaceship is not stopped. The spaceship does not suffer the force of attraction or force of repulsion due to the planets or stars as the gravitational force is not acting on the spaceship.

Therefore, the correct answer to this problem is option B.

Additional information:
In space, due to the absence of any atmosphere, we cannot hear any sound as in order to hear the sound we need an atmosphere as sound needs a medium to transfer its energy as it shows particle nature. Light does not need an atmosphere and therefore the light from the sun easily reaches the earth’s surface. The atmosphere on the earth creates a huge air drag to the airplanes and this is why the planes come to rest if continuous combustion of fuel is not done.

Note:
The net external force on the spaceship is the force produced due to the combustion of fuel. There is no atmosphere to hold the spaceship back and no air drag. The main factor is that the gravitational force on the spaceship is zero.