Important points :-
1:- Kinetic energy (KE) doesn’t depend upon direction of motion & it is never negative.
2:-As velocity is a frame depend quantity therefore KE also depends on reference frame.
3:-KE of a system can be increased or decreased without applying any external force of the system by the use of internal energy. For eg- bomb.
4:-Work done (WD) by all Forces on a system equal the change in KE.
5:-Work done by external force on a system equals the change in its total energy (TE).
6:-Negative of the WD by the conservative internal force on a system equals to change in PE.
7:-NO work is done by a force on an object if-
- The force is always perpendicular to its velocity.
- The object is stationary but the point of application of the force moves on the object.
- The object moves in such a way that the point of application of the force remain fixed.
8:-Work, Energy theorm depends upon reference frame.
9:-Body can have mechanical energy without having momentum & also can have momentum without mechanical energy. i.e. [ KE=O , TE=PE][KE =-PE, TE=O].
10:-It is possible to exert a force which does work on a body without changing its KE.
11:-In spring block system maximum velocity is when (Fnet = O or a=o ) is at mean position.
12:-If a block of mass M slides down a plane inclined at an angle ∅ increasing the angle will not increase the energy lost due to friction.
13:-When a conservative force does the positive (+ive ) work on a body the PE decreases.
14:-PE of a simple pendulum is Max when it is the turning points of the oscillation.
- WD by gravity is negative (-ive ) that mean PE increases & KE decreases.
- Positive WD means KE & P(momentum) both increases.
15:-Mechanical energy of a body can be negative if PE>KE
16:-It is physically not possible to have situation when (E-U<O)
17:-Internal force can change KE & ME but can’t change the TE & MOMENTUM.
18:-When two particle collide and stick together only energy is conserved & work is negative. As ME & KE is not conserved.