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Exercise Numerical
Chapter 6 of Class 9 Physics focuses on Work and Energy, two fundamental concepts in physics that describe the ability to do work and the transfer of energy in various forms.
Key Concepts:
- Work: The chapter begins with the definition of work as the product of force and displacement in the direction of the force. Mathematically, work (WWW) is expressed as:W=F×d×cos(θ)W = F \times d \times \cos(\theta)W=F×d×cos(θ)where FFF is the force applied, ddd is the displacement, and θ\thetaθ is the angle between the force and displacement vectors. Work is measured in joules (J).
- Types of Work: The chapter distinguishes between different types of work:
- Positive Work: When the force and displacement are in the same direction.
- Negative Work: When the force and displacement are in opposite directions.
- Zero Work: When the displacement is zero or the force is perpendicular to the displacement.
- Energy: Energy is defined as the capacity to do work. The chapter introduces various forms of energy, including:
- Kinetic Energy (KE): The energy possessed by an object due to its motion, calculated as: KE=12mv2KE = \frac{1}{2} mv^2KE=21mv2 where mmm is the mass and vvv is the velocity.
- Potential Energy (PE): The energy stored in an object due to its position or configuration, commonly gravitational potential energy given by: PE=mghPE = mghPE=mgh where hhh is the height above a reference point, and ggg is the acceleration due to gravity.
- Law of Conservation of Energy: The chapter discusses the principle of conservation of energy, which states that energy cannot be created or destroyed, only transformed from one form to another. The total mechanical energy (kinetic + potential) of a closed system remains constant.
- Power: Power is introduced as the rate at which work is done or energy is transferred, defined as:P=WtP = \frac{W}{t}P=tWwhere PPP is power, WWW is work, and ttt is the time taken. Power is measured in watts (W).
This chapter provides a foundational understanding of work and energy, essential for exploring more complex concepts in physics, such as mechanical systems and energy transformations in various contexts.