Why do we use a spaceship in outer space, far from other objects, to illustrate Newton's first law? Why not a car or a train? (More than one of the following statements may be correct.) ($\mathbf{1}$) A car or train touches other objects, and interacts with them. ($\mathbf{2}$) A car or train can't travel fast enough. ($\mathbf{3}$) The spaceship has negligible interactions with other objects. ($\mathbf{4}$) A car or train interacts gravitationally with the Earth. ($\mathbf{5}$) A spaceship can never experience a gravitational force.

According to Newton’s First Law of motion, if a body is at rest it will remain at rest or if a body is in motion it will remains in motion unless it is compelled by any external force.

Cars or trains are always in contact with roads or railway tracks. So, contact forces are present. Significant interaction is present between cars or trains and other objects. Therefore, cars or trains are not used to illustrate Newton’s first law. Hence the statement (1) is true.

It is true that cars or trains can’t travel fast enough compared to a spaceship. But speed is not a factor which is used to illustrate Newton’s first law. It is illustrated by the contact forces present between objects. So, speed of the body does not matter. Hence the statement (2) is false.

The spaceship is present in vacuum. There is no environment there. Hence, there is no interaction with other objects. So, Newton’s first law can be illustrated. Hence the statement (3) is true.

Cars or trains are under the gravitational pull of earth. Therefore, interaction is present between earth and these bodies. This is the reason Newton’s first law is generally not illustrated by these bodies. Hence the statement (4) is true.

A spaceship may experience gravitational force when it is close to a certain planet. It is not necessary that a spaceship can always be used to illustrate Newton’s first law due to this reason. Hence the statement (5) is false.

Thus, out of all, the true statements are (1), (3) and (4).