Introduction to Work Energy Theorem

• Work Energy Theorem: It states that the work done on a system is stored as energy within it.
• Example: When a person lifts a box, the work done is stored as potential energy in the box.

Principle of Work Energy Theorem

• Proof: The proof of the work energy theorem shows that the work done by the net force is equal to the change in kinetic energy of the system.
• Formula: ( W = \Delta KE = KE_{final} - KE_{initial} )

Application of Work Energy Theorem

• Work done = Change in kinetic energy of the system
• Supporting Force causes an increase in kinetic energy.
• Opposing Force causes a decrease in kinetic energy.

Numerical Problem

1. Example 1: Calculate the average frictional force during car braking.

   • Initial Speed: 72 km/h = 20 m/s
   • Distance: 25 meters
   • Mass: 500 kg
   • Solution: Weight = mass; Retardation = -8 m/s²; Average Frictional Force = 4000 Newtons

2. Example 2: Calculate work for a particle's velocity.

   • Using Change in Kinetic Energy
   • Work Done = 200 Joules

Important Points

• Stated Work Energy Theorem: Work done on a system brings an equivalent change in its kinetic energy.
• Importance of Education: Taking notes is important so that things are remembered for the long term.

Conclusion

• Various problems can be solved using the work energy theorem.
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