A car of mass 1.2 tonnes is travelling along a straight horizontal road at a speed of 20 ms' when it brakes sharply then skids. Friction brings the car to rest. If the coefficient of friction between the tyres and road is
0.8, calculate the distance travelled by the car before it comes to rest.​

The sun’s mass is 2.0×10^ 30 kg, its radius is 7.0×10 5 km, and it has a rotational period of approximately 28 days. if the sun should collapse into a white dwarf of radius 3.5×10 3 km, what would its period be if no mass were ejected and a sphere of uniform density can model the sun both before and after?