In mechanics, speed increase is the pace of progress of the speed of an article regarding time (acceleration). Speed increases are vector amounts (in that they have greatness and direction). The direction of an item's speed increase is given by the direction of the net power following up on that article. The size of an item's speed increase, as depicted by Newton's Second Law, is the consolidated impact of two causes:
the net equilibrium of all outer powers acting onto that item — size is straightforwardly relative to this net coming about force;
that article's mass, contingent upon the materials out of which it is made — extent is conversely relative to the item's mass.
First way: The definition of the acceleration states that an object accelerates when it <u>has a force applied to it</u>
Second way: The definition of the acceleration states that an object accelerates when it <u>changes its velocity</u>
<u></u>
<u><em>Reasons</em></u>
<u><em>For the first way</em></u><em>, by newton's second law, force equals to the product of mass times acceleration. The mass of the objects stays constant thus it is a constant in this equation. Thus when the Force isn't zero or bascially when it is applied, then the object must accelerate</em>
<u><em>For the second way</em></u><em>, acceleration is the rate of change of velocity, thus as velocity changes, the object must be accelerating</em>
Well all reactions need energy to start it. The light is the energy that the reaction requires to start it. Sunlight also has no mass in the first place so laws of conservation of mass don't apply to it.