Which of the following is NOT true about chemical changes? -They are not easily reversible
-They often happen faster at higher temperatures
-At least one new substance is formed that has different chemical properties
-The substance changes form but stays the same substance

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

Does work output exceed work input when a machine is used? a) yes, it does, as machines create energy. b) it depends on the type of machine used. c) no, it doesn’t, as machines are inefficient. d) no, it doesn’t, as machines cannot create energy.

Which of the following is an example of motion in two dimensions?