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Understanding Momentum and Energy in Physics

Learn about momentum as "inertia in motion" and energy as the ability to do work. Explore concepts like impulse, conservation laws, potential and kinetic energy, and power in this insightful chapter.

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Understanding Momentum and Energy in Physics

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  1. Chapter 5 Momentum and Energy

  2. Momentum: • By Momentum, we mean “Inertia in Motion” or more specifically, the mass of an object multiplied by its velocity. • Momentum = mass × velocity • or in shorthand notation, • Momentum = m × v • P = m × v • When direction is not an important factor, we can say • Momentum = mass × speed • S.I Unit of Momentum : • Kg-m/sec or N-sec

  3. Impulse Changes Momentum: The greater the impulse exerted on some thing, the greater the change in momentum. The exact relationship is, • Impulse = Change in Momentum • or in shorthand notation, • Ft = Δ(mv) • Where Δ is the symbol for “change in”

  4. Law of Conservation of Momentum P1(initial) + P2(initial) = P1(final) +P2(final) If no net external force acts on a system, the total linear momentum of the system cannot change. Or It can be stated that The sum of a system's initial momentum is equal to the sum of a system's final momentum. The law of conservation of momentum can be mathematically expressed as Total momentum before collision = Total momentum after collision

  5. Energy: “The ability of a body to do work is called Energy’’ • S.I Unit of Energy: • joules

  6. Energy and Work:“Work is the product of force and distance.’’ • Work = Force × Distance • or in shorthand notation, • W = F d • S.I Unit of Work: • joules

  7. Potential Energy:“The Energy stored by an object by virtue of its position is called Potential Energy (P.E)” or in shorthand notation, • P.E = mgh • S.I Unit of P.E: • joules

  8. Kinetic Energy:“The Energy of motion is called Kinetic Energy (K.E)”or in shorthand notation, • S.I Unit of K.E: • joules

  9. Conservation of Energy: “The energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.”

  10. Conservation of Energy

  11. Power: Rate of doing work Or Work done per unit time Unit- Watt= Joule/sec Horse power (hp) English system 1hp= 746 Watt

  12. Examples • An elevator with a person inside weighs 5000 N. If it is raised to a height of 15 m in 10 sec. Find (a)The work done on the elevator by the motor. (b)The power • 100 Watt lamp

  13. End of the Chapter

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