3. The mass of a planet is twice that of Earth. Its radius is half that of the radius of Earth. The gravitational field strength at the surface of Earth is g. The gravitational field strength
at the surface of the planet is?

Olympic skier tina maze skis down a steep slope that descends at an angle of 30∘ below the horizontal. the coefficient of sliding friction between her skis and the snow is 0.10. i found maze's acceleration which is 4.1 m/s^2. but how do you determine maze's speed 4.0 s after starting?