# AP Inter 1st Year Physics Notes Chapter 6 Work, Energy and Power

Students can go through AP Inter 1st Year Physics Notes 6th Lesson Work, Energy and Power will help students in revising the entire concepts quickly.

## AP Inter 1st Year Physics Notes 6th Lesson Work, Energy and Power

→ The scalar product (or) dot product of any two vectors A and B denoted as A.B = AB cos θ.

→ The dot product of A and B is a scalar.

→ Dot product obey’s commutative law. $$\vec{A} \cdot \vec{B}=\vec{B} \cdot \vec{A}$$

→ Dot product obeys distributive law $$\vec{A} \cdot(\vec{B}+\vec{C})=\vec{A} \cdot \vec{B}+\vec{A} \cdot \vec{C}$$

→ The work done is a scalar quantity. It can be positive (or) negative.

→ Work done by the friction (or) viscous force on a moving body is negative.

→ The work – energy theorem states that the change in K.E of a body is the work done by the net force on the body.
Kf – Ki = WNet

→ The work-energy theorem is not independent of Newtons second law.

→ The work-energy theorem holds in all internal forces.

→ The P.E of a body subjected to a conservative force is always undetermined upto a constant.

→ Work done by friction over a closed path is not zero and no potential energy can be associated with friction.

→ The energy possessed by a body by virtue of its position (or) state is called potential energy. V(h) = mgh, if h is taken as variable.

→ The energy possessed by a body by virtue of its motion is called kinetic energy
K = $$\frac{1}{2}$$mv2.

→ Work done by a variable force W = $$\int_{x_1}^{x_1} F(x)$$

→ The total mechanical energy of a system observed if the forces, doing work on it, are conservative.

→ The spring force is a conservative force.

→ Eiitstein mass-energy relation is E = mC2
Where C = 3 × 108 m/s = Velocity of light

→ The rate of doing work is called power, Pav = $$\frac{W}{t}$$

→ Another unit of power is horse – power (HP) 1 H.P = 746 W.

→ Collision is an interaction between two (or) more bodies in which sudden changes of momenta take place.

→ In an elastic collision both K.E. and linear momentum are conserved.

→ A collision in which only momentum.is conserved but not the K.E is called inelastic collision.

→ Coefficient of restitution (e) = $$=\frac{\text { Relative velocity of separation }}{\text { Relative velocity of approach }}$$