CG Board Class 6 Science Work Energy and machines Notes / Textbook Exercises / Question Answers as well as Additional Question Answers from the Chapter.
Definition of Work:- The product of force applied to an object and displacement in the direction of that force is work. This definition is different from the everyday use of the word “work.”
Units of Work and Energy: The standard unit of work and energy in the International System (SI) is the Joule (J).
Types of Energy: Mechanical Energy: Mechanical energy can be in the form of potential energy or kinetic energy, depending on the body’s position or motion.
Chemical Energy: Chemical reactions can release energy stored in fuel, food, and batteries.
Thermal Energy: Heat energy is a form of energy that has the ability to do work, such as in steam engines.
Light Energy: Visible light energy can be converted into electricity, like in solar cells.
Sound Energy: When a body vibrates, it produces energy that can be transformed into mechanical or electrical energy.
Electric Energy: Electric currents carry energy that is utilized by a wide range of electrical appliances and devices.
Energy Conservation: The conservation of energy law states that energy cannot be created or destroyed, only transformed from one form to another. This principle is fundamental to physics.
Machines: Machines are devices that make work easier by multiplying force, changing the direction of force, or both. Examples of simple machines include levers, inclined planes, wedges, screws, pulleys, and wheel and axle.
Levers: Levers are simple machines that consist of a rigid bar (lever arm) and a fulcrum. There are three types of levers:
Lever of the First Kind: Fulcrum is between the load and the effort.
Lever of the Second Kind: The load is between the fulcrum and the effort.
Lever of the Third Kind: The effort is between the load and the fulcrum.
Inclined Plane: An inclined plane is a flat surface set at an angle to the horizontal. It’s used to raise or lower objects with less effort.
Wedge: A wedge is a simple machine consisting of two inclined planes used for various tasks such as cutting, tearing or separating objects.
Screw: A screw is an inclined plane wound around a cylindrical pin, used for fastening and lifting.
Pulley: A pulley is a simple machine consisting of a wheel on an axle, used to change the direction of force and make lifting objects easier.
Wheel and Axle: The wheel and axle is a simple machine where a cylindrical wheel is attached to a smaller cylinder (the axle), allowing for the transfer of force.
Units of Measurement: The unit of work and energy is the Joule, while different forms of energy (e.g., chemical energy) are associated with various substances and processes.
Choose the correct alternative
1. Is a simple machine
a.cycle
b. tractor
c. forceps
d. sewing machine.
2. A scissor is a lever of which kind?
a. first
b. second
c. third
d. none of these.
3. Which of the following work, machines cannot do?
a. Apply force at a convenient point
b. Increase the speed
c. Change the direction of force
d. Produce energy
4. Joule is a unit of
a. Work
b. Energy
c. Work as well as energy
d. Neither of work nor of energy.
5. Petroleum products have energy in the form of –
a. Chemical energy
b. Electric energy
c. Light energy
d. Sound energy
Fill in the blanks: –
1. Tractor is a ___________ machine.
2. Fulcrum is in the middle for levers of the ____________ kind.[second]
3. In the lever of the second kind, ________________is in between the fulcrum and effort.[load]
4. The spade used to lift garbage is a lever of the ______________ kind.[third]
5. The use of planks to lift drums on a truck is an example of ___________________.[inclined plane]
6. In the extended rubber of a catapult ______________ energy is stored.[potential]
Answer the following questions : –
1. What is a machine?
A machine is a device that helps make work easier by either multiplying the force applied, changing the direction of the force, or both. Machines are designed to perform specific tasks efficiently.
2. What is known as a lever?
A lever is a simple machine consisting of a rigid bar that can rotate around a fixed point called the fulcrum. Levers are used to lift or move objects by applying force at one end of the bar, which causes the other end to move and exert force on the object.
3. How are fulcrum, load and effort placed in different kinds of levers?
Lever of the First Kind: Fulcrum is between the load and the effort.
Lever of the Second Kind: The load is between the fulcrum and the effort.
Lever of the Third Kind: The effort is between the load and the fulcrum.
4. What is work? Write the units of work.
Work is done when a force is applied to an object, and the object is displaced in the direction of the applied force. The unit of work is the Joule (J) in the International System (SI).
5. If a body moves a distance of 12 metres on applying a force of 125 newton, compute the amount of work done.
Work (W) = Force (F) × Distance (d)
W = 125 N × 12 m
W = 1500 Joules (J)
Therefore, the amount of work done is 1500 Joules.
6. Define energy. What is the relation between work and energy?
Energy is the ability to do work or cause a change in a system. Work and energy are closely related. When work is done on an object, energy is transferred to or from that object. The work-energy theorem states that the work done on an object is equal to the change in its energy. In other words, work is a means of transferring energy between systems.
7. Write five types of energy. Give examples of each.
Mechanical Energy: Examples – moving car .
Chemical Energy: Found in fuels like gasoline and food.
Thermal Energy: Heat energy, like a boiling kettle.
Light Energy: light bulb.
Sound Energy: ringing bell or musical instruments.
