How do a bone turn into a fossil?

Suppose you use a machine that gives you a mechanical advantage of 2 to achieve an output force of 30newtons what must the input force be

Aplane flies directly between two cities, a and b, which are separated by . from a to b, the plane flies into a headwind. on the return trip from b to a, the wind velocity is unchanged. the trip from b to a takes less than the trip from a to b. what is the airspeed of the plane, assuming it is the same in both directions

Which type of wave can travel without a medium