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[accordion title=”1. Newton’s Laws of Motion”]

**Newton’s First Law**: a body will remain in its state of rest or uniform motion in a straight line unless acted upon by a resultant force.
**Newton’s Second Law**: ** **the rate of change of momentum of a body is proportional to the resultant force acting on it and the change takes place in the direction of the resultant force.
- $$F =\frac{dp}{dt}$$ in general
- $$F =ma$$ when mass is constant.

**Newton’s Third Law**: if body A exerts a force on body B, then body B exerts an equal and opposite force on body A

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[accordion title=”2. Linear Momentum”]

- The
**linear momentum** of a body is defined as the product of its mass and its velocity.
**Impulse **is the product of the force acting on a body and the time interval during which the force is exerted. It is equal to the change in momentum of the body.
- For constant force, impulse = $$\Delta p =F \Delta t$$
- In general, impulse = $$\Delta p =\int {F .dt}$$

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[accordion title=”3. Collision Problems”]

- The principle of
**conservation of momentum** states that the total momentum of a system of colliding objects remains constant provided no resultant external force acts on the system.
**Conservation of momentum** applies to both **elastic** and **inelastic **collisions.
- $$m_1u_1+m_2u_2=m_1v_1+m_2v_2$$

**Conservation of kinetic energy **applies only to elastic collisions.
- $$\frac{1}{2}m_1u_1^2+\frac{1}{2}m_2u_2^2=\frac{1}{2}m_1v_1^2+\frac{1}{2}m_2v_2^2$$

**Relative speed of approach = Relative speed of separation**

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