FORCE WORK AND ENERGY CLASS 4 CBSE

OWNER: DEEPA UNNIKRISHNAN
CLASS 4 SCIENCE

1. Force, Work and Energy Class 4 Science

2. Force Part 1

3. What is force ? A force is a push or a pull on an object that is caused by an interaction with another object.

4. Effects of force A force can move a stationary object. A force can slow down or stop a moving object. A force can change the speed of a moving object. A force can change the direction of a moving object. A force can change the shape and size of an object.

5. Types of force Gravitational Force : Gravitational force or gravity is the force that attracts objects to the centre of the Earth.

6. GRAVITY Example When a ball is thrown in the air, it comes back towards the earth due to gravitational force, an apple falling from a tree, etc. Force off gravity is acting on an object even when the object is at rest.

7. Types of force Frictional force or friction : Frictional force or friction is the force that tries to stop the movement of objects across a surface. Friction always acts in the direction opposite to the direction of movement of an object.

8. FRICTION The force that is present when two things are in contact with each other is called a friction. This force resist the motion of an object on the surface. As a result ,the object either slows down or stops moving. Materials with a smooth surface ( Eg. glass or ice) causes less friction than materials little rough surface . Eg. carpet.

9. Recap time 1) The force that pulls objects toward the center of the Earth is called: a. a push or pull b. friction c. mass d. gravity 2) Something that makes objects start moving, stop moving, slow down or change direction is a: a. a push or pull b. friction c. mass d. gravity

10. Recap time 3) Which of the following surfaces has the least amount of friction? a. a gravel driveway b. a dirt road c. a road covered with ice d. a road covered with spilled sand 4) Megan throws a paper airplane. How will gravity make the airplane move? A.in a straight line B.up toward the sky C. back toward Megan d. down toward the ground

11. WORK Work is said to be done only when the force applied an object cause it to move through a distance or a change in the shape or size of that object . Eg : The football moves, when a child kick it .

12. Simple machines Machines are simple tools which make our work easier and faster with use of less energy. They help us to do many works.

13. Types of simple machines There are 6 types of simple machines:- Lever Pulley Inclined plane Wheel and axle Screw Wedge

14. 1. Lever A lever is a simple machine that is made up of rod resting at a point around which it moves. It is used to lift or move heavier weights , cut things or open the lid of a tin. Eg : a pair of scissors , see-saw, bottle openers, paper cutter etc.

15. Pulley A simple pulley is a wheel with a groove along its edge, for holding a rope or a chain. It is used to lift heavy objects attached to one end of the rope Eg - Pulley is used to pull water from a well .

16. Wheel and Axle Wheel and axle is a simple machine. It is used to move a heavy load using less effort. It consists of a wheel rigidly attached to a rod (called axle). When one rotates the wheel, the axle also rotates.

17. Inclined Plane An inclined plane is a sloping surface daddy issues are to push or pull heavy objects to a certain height . It makes it easier to lift a heavy object. It is easier to pull or roll an object up an inclined plane than to lift it directly. Eg - A sloping plank is used while loading barrels into a truck. Inclined plane is used in hospitals to push up the wheelchair.

18. SCREW Types of Inclined Plane 2. WEDGE

19. Types of Inclined Plane SCREW A screw is actually an inclined plane wrapped around a cylinder that has a sharp pointed end. Screw helps to attach things to each other. Screws are turned with the help of a screwdriver. As they rotate they also move forward. 2.WEDGE A wedge has at least one incline plane ending in a sharp edge. This sharp edge helps to cut things.

20. Energy and its Resources Part - 3

21. Energy

22. What is Energy ? The ability to do work is called energy. There are many forms of energy

23. Types of energy Heat energy light energy solar energy Wind energy Hydroenergy sound energy geothermal energy mechanical energy electrical energy

24. Forms of energy Heat energy : Burning fuels such as coal, LPG, and kerosene release heat energy. In our homes, we use heat energy to cook food.

25. Forms of energy Light energy : Light energy helps us to see things around us. Electric bulb, lamp, tube light, and candle are some sources of light energy. The sun is also a source of light energy.

26. Forms of energy Solar energy: The energy that we get from the sun is called solar energy. It is used to provide heat, light, hot water, and electricity.

27. Forms of energy Wind energy : Power of the moving air (wind) is utilized with the help of windmills to generate electrical energy.

28. Hydro energy Moving water also has a lot of energy in it. this energy is called hydro energy. to use this energy, we build dams. these dams allow the water to fall from a height onto turbines with great force. then turbines move and helps to produce electric energy.

29. Forms of energy Sound energy: Portable audio players, television, radio, and loudspeakers are sources of sound energy. Musical instruments such as guitar and tabla also produce sound energy.