Force, Work, and Energy

Class V - science: Force, Work and Energy
One Word Answer Questions:
Q) A push or pull of an object is called? A)    Show/hide Answer

Q) What we need to move an object?
A)    Show/hide Answer

Q) Which force slows down the movement of the object?
A)    Show/hide Answer

Q) In which of the following activity, work is said to be done?
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Q) Give one example of lever? A)    Show/hide Answer

Q) Output of a truck is 4500 J and its efficiency is 50%, input energy provided to truck is?
A)    Show/hide Answer

Q) The gravitational force was first discovered by?
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Q) Examples of third class levers are?
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Q) A force can change?
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Q) The energy stored in a body due to its position is called?
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Short Answer Questions:
Q) What are the effects of force?
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Q) What is pull and push?
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Q) What is Wedge and Compound machines?
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Q) What is screw, wheel and axle?
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Q) What is pulley and Inclined plane?
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Q) Explain briefly about lever?
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Q) Explain briefly about Classes of levers?
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Q) Explain briefly about Energy?
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Q) Explain briefly about Solar Energy?
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Q) Explain briefly about Wind Energy?
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Long Answer Questions:
Q) what are the advantages and disadvantages frictions?
A)   Show/hide Answer

Q) Explain about force?
A)   Show/hide Answer

Q) Explain about work?
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Q) Explain about energy?
A)   Show/hide Answer

Q) Explain about simple machines?
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Q) Explain in detail about levers? and explain about Classes of levers?
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Q) Explain in detail about Solar Energy and Wind Energy?
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Q) Explain in detail about Effects of force?
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Q) Explain in detail about Types of force?
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Q) Explain in detail about Advantages and Disadvantages of frictions?
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### Force

• A push or pull on an object. ### Effects of force:-

#### 1). A force can stop a moving objects:-

• If force is applied on an object in opposite direction.
• It can slow down.
• To Stop a moving object.
• Eg:- Force applied by a player on moving football, to stop the ball.

#### 2). A force can move a stationary object:-

• Apply force on a stationary object, it can move it in the direction of force.
• Eg:- A player can move a football by kicking it.

#### 3). A force can change the direction:-

• When force is applied on the opposite direction on a moving ball it can change the direction.

#### 4).A force can change the shape of an object:-

• A force can also change the shape of an object.
• Ex:- When we press a balloon full of air, it changes its shape.
• When we make bread, the force of our hands changes the shape of dough.

### Types of force:-

Magnetic force Electric force Gravity or gravitational force Frictional force
• Force applied by a magnet on an object is called magnetic force.
• When things are rubbed with each other, they become charged and a force of attraction is produced.
• This force is called electrostatic force.
• This force may also be repulsive.
• Earth exerts a force on every object that attracts towards the centre of earth.
• This is called gravitational force.
• Ex:- fruit falling from a tree.
• Force that slows down the movement of object across a surface is called force of friction also called force of resistance.

### Advantages of frictions:-

1. Helps us to walk on a smooth surface or wet floor friction is very less and we may slip over the floor.
2. Friction between road and tyres of automobiles makes their movement possible.
3. Able to write with our pen. Cannot write easily on a oily paper because of less frictions between pen and oily paper.
4. Frictions helps to erase pencil marks from the paper by using eraser.

### Disadvantages of frictions:-

1. Hinders the motion of vechicles.
2. Produces heat, that damages the machines, hence we use oil.
3. Frictions damages the tyres of vehicles and soles of our shoes.

### Work

• Work is said to be done, only when the applied force causes a change in the position of the objects in the direction of the applied force. ### Energy

• The ability to do work is called energy. ### Heat Energy:-

• Energy that we get from heat is called heat energy.
• Produced by burning fuels like coal, LPG and kerosene.
• We use this energy to cook food. ### Light Energy:-

• Energy that we get from light is called light energy.
• Produced by bulb, candle etc.
• We are able to see with the help of light energy.

### Kinetic energy:-

• Energy of an object due to its movement is called kinetic energy.
• Eg:-Moving cycle, running boy. ### Potential Energy:-

• Energy stored in a body due to its position is called potential energy.
• Eg:-Water stored in tank.

### Mechanical Energy:-

• Combination of potential & kinetic energy.
• Ex:-water stored behind a dam has potential energy and when it falls changes to kinetic energy. ### Electrical Energy:-

• The energy that we get from electric current is called electric energy.
• Appliance run line, Tv, washing machine etc
• Generated at power stations and supplied to our homes.

### Wind Energy:-

• Moving air is called wind.
• Has power to move things called wind energy.
• Used to generate electricity by using a wind mill. ### Solar Energy:-

• Energy of the sun is called solar energy.
• Used to cook food in solar cookers.
• Heat water in solar heater.
• Solar calculators, solar watches.

### Simple Machines

• Is a device that makes our work easier and faster.
• Eg:-Scissors, knives, tweezers and tongs.

Simple machines are grouped as

### Lever:-

• A simple machine that turns around a fixed point is called lever.
• Helps us to do more work by applying less force.
• Makes work easier.
• 3 parts load, effort and fulcrum.
1. Load(L):- The object on which work is to be performed.
2. Effort(E):- The force applied on a lever to lift or move the load is called effort.
3. Fulcrum(F):- Fixed point on which a lever turns. ### Classes of levers:-

• Mainly three classes of levers depending on the positions of the load(L).

#### 1) First class lever:-

• Fulcrum(F) is between the load and effort.
• Eg:- Crowbar, see-saw, scissors, spoon. #### 2) Second class lever:-

• Load(L) is between the fulcrum and effort.
• Ex:- Weel-barrow, nutcracker, bottle cap-opener etc #### 3)Third class lever:-

• The effort (E) is in between the fulcrum and load.
• Ex:-Forceps, ice tongs, knife, staple machine, etc

### Pulley:-

• A pulley is a wheel with a groove in its rim. The rope moves through this groove.
• Ex- Water is drown from a well using a bucket tied to a long rope.
• When we lift the bucket of water from the well by pulling the rope vertically upwards it is a difficult job.
• With the help of a pulley we can easily draw water from the well. ### Inclined plane:-

• A simple machine that has a sloping surface is called a inclined plane.
• Ex- ramps, sloping wooden planks, slides etc. ### Screw:-

• Looks like a nail with grooves cut into it.
• Has a winding edge called a thread can hold things together tightly.
• Ex:- Screw jack.

### Wheel and axle:-

• Simple machine consists of a wheel and a rod called axle. Wheel and axle rotates together.
• Ex-Screw driver, car steering, tap sewing machine. ### Wedge:-

• V-shaped piece, made up of metal.
• Has two inclined planes. Put together to form a sharp edge.
• Ex-axe, blade & knife used to cut and split things. ### Compound machines:-

• If a clock is opened, you can see several simple machines inside it.
• The cars, aeroplanes, sewing machines consists of several machines.
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