Class 9th · Physics · Chapter 5
Chapter 5: Work, Energy and Power
Chapter 5 of the Punjab Board Class 9th Physics textbook runs from page 105 to 126 and covers 4 topics. Its exercise has multiple choice questions, short / constructed response questions, comprehensive questions and numerical problems. Open any of those pages in GenZ Books, tap a question, and the answer is worked from this chapter.
Open Chapter 5 of Physics in GenZ Books
The same Class 9th textbook, page for page. Tap any question and get the answer worked from that chapter — English and Urdu.
What you will learn
- * Defineworkdone. * Use the equation work done = force x distance moved in the direction of the force W=F x dtosolve problems * Define energy asthe ability to do work * Explain that energy may be stored [Such as in gravitational potential, chemical, elastic (strain), nuclear, electrostatic, and internal (thermal) energies] * Prove that Kinetic Energy= + mv’ [use of equations of motion not needed; proof through kinematic graphs will suffice]
- Prove and use the formula for٭ gravitational potential energy Use the formulas for kinetic and gravitational potentialenergy to solve problems involving٭ simple energy conversions [make use of the Conversion of energy from one form to the other, including cases involving loss of energytothe surroundings] * Describe how energy is transferred and. stored during events and processes [e.g. work done during transfer by mechanical wotkdone, electrical work done, and heat] * State and apply the principle of thecenservation of energy * Justify why perpetual energy machines do not work * Differentiate between and listrenewable and non-renewable energy sources * Describe how useful energy.may
Topics in this chapter
- 5.3Conservation of Energyp. 112
- 5.4Sources of Energyp. 113
- 5.5Renewable andp. 117
- 5.8Efficiencyp. 121
Exercise
- Multiple Choice Questionsp. 123
- Short / Constructed Response Questionsp. 124
- Comprehensive Questionsp. 125
- Numerical Problemsp. 125
A sample answer from GenZ Books
Solve · page 108: A person does 200J of workin pushing a carton through a distance of 5 metres. How much force is applied by him?
Solution
- Write the formula for work when the force is along the direction of motion (Eq. 5.1 in the book)
$$ W = F \times S $$
where
- $W$ = work done (Joules, J)
- $F$ = magnitude of the applied force (Newtons, N)
- $S$ = distance moved in the direction of the force (metres, m)
- Re‑arrange the formula to find the unknown force
$$ F = \frac{W}{S} $$
- Substitute the given values
$$ F = \frac{200\ \text{J}}{5\ \text{m}} $$
- Calculate
$$ F = 40\ \text{N} $$
Answer: $F = 40\ \text{N}$
Check: Multiply the obtained force by the distance: $40\ \text{N} \times 5\ \text{m} = 200\ \text{J}$, which matches the given work.
AI-generated from the chapter text by GenZ Books. It can make mistakes — check it against your textbook and your teacher.