Final answer:
The force acting on a ball thrown upward on Mars is gravity. Friction or magnetic force are not applicable as they require specific conditions or materials. 'No force' is not accurate since the gravitational force is always present.
Step-by-step explanation:
When you throw a ball upward with a velocity of m/s on Mars, the primary force acting on the ball is gravity. On Mars, just like on Earth, gravity pulls objects towards the planet's surface. However, the gravitational acceleration on Mars is different from that on Earth. Since the velocity is given but the exact number is not indicated (as 'm/s' is not a complete value), we cannot calculate the exact force without the correct velocity value or the gravitational acceleration value specific to Mars.
According to Newton's First Law of Motion, a body in motion will remain in motion unless acted upon by an external force. In this scenario, the external force is Mars's gravitational pull. The options provided include 'Gravity' and we can confidently select this as the correct answer.
Other forces like friction, magnetic force, or 'No force' are not relevant here. Friction mainly comes into play when objects are in contact with a surface, magnetic force would only be applicable in the presence of a magnetic field and materials that interact with it, and 'No force' does not apply since gravity is always present for objects with mass.