Samacheer Kalvi Class 4 Science Solutions Term 1 Chapter 3 Work and Energy

I. Use the Correct Word to Fill the Blanks:

 

Question 1. _________ is said to be done when a force is acting on it.
Answer: Work is done when a force acts on an object and makes it move. This happens when effort is applied to cause movement.
In simple words: When you push or pull something and it moves, that is called work.

🎯 Exam Tip: Remember, work needs both a force and movement in the direction of the force.

 

Question 2. The ability to do work is _________.
Answer: The ability to do work is called energy. You need energy to perform any task, big or small.
In simple words: Energy is what lets you do things, like playing or studying.

🎯 Exam Tip: Energy is essential for all activities, whether it's moving objects or powering machines.

 

Question 3. _________ is a machine made up of wheel and rope.
Answer: A pulley is a simple machine that uses a wheel and a rope to lift heavy things. It helps change the direction of force and makes lifting easier.
In simple words: A pulley is a tool with a wheel and rope, used to lift heavy items easily.

🎯 Exam Tip: Pulleys are common in everyday life, from flagpoles to window blinds, helping us manage heavy loads.

 

Question 4. _________ help us to make work easier.
Answer: Simple machines help us make work easier by changing the amount or direction of force. Examples include levers, pulleys, and ramps.
In simple words: Simple machines are tools that make tough jobs feel less hard.

🎯 Exam Tip: Simple machines are the basic building blocks of all complex machines.

 

Question 5. An example for inclined plane is _________.
Answer: A ramp is a good example of an inclined plane, which is a flat surface tilted at an angle. It helps move objects to a higher or lower place with less effort.
In simple words: A ramp is like a sloped path that makes it easier to go up or down.

🎯 Exam Tip: Inclined planes reduce the force needed to move an object vertically, but increase the distance over which the force must be applied.

II. Rearrange the Letters and Find Out the Names of the Tools:

 

Question 1. Rearrange the letters EDGEW to find the name of the tool shown in the picture.
Answer: WEDGE
In simple words: The mixed-up letters spell out "WEDGE," which is what the tool in the picture is.

🎯 Exam Tip: Look at the image carefully and try different letter combinations to form the word, focusing on common tool names.

 

Question 2. Rearrange the letters RLEVE to find the name of the tool shown in the picture.
Answer: LEVER
In simple words: The jumbled letters form the word "LEVER," which describes the tool.

🎯 Exam Tip: Pliers are a type of lever, where the pivot (fulcrum) is between the effort and the load.

 

Question 3. Rearrange the letters EWCRS to find the name of the tool shown in the picture.
Answer: SCREW
In simple words: The mixed-up letters spell "SCREW," which is the tool shown.

🎯 Exam Tip: A screw is an inclined plane wrapped around a cylinder, used to fasten things together or lift objects.

III. Match the Following:

 

Question 1. Match the following:
1. Class II lever
2. Pulley
3. Class I lever
4. Wheel and axle
5. Renewable resource
Answer:
1. Class II lever - Nut cracker
2. Pulley - Drawing water
3. Class I lever - Seesaw
4. Wheel and axle - Bicycle
5. Renewable resource - Wind
In simple words: Match each machine or resource type with its correct example. For example, a nut cracker is a Class II lever.

🎯 Exam Tip: To score full marks, know the definitions and classic examples for each simple machine and energy resource.

IV. Classify the Things Below: (Text Book Page No. 109)

 

Question 1. Classify the things below:

Answer:
In simple words: Understand how levers are grouped based on where the fulcrum, load, and effort are located. Then, apply this knowledge to classify each given example.

🎯 Exam Tip: Practice classifying various tools as Class I, II, or III levers by identifying the positions of the fulcrum, effort, and load.

V. Answer the Following:

 

Question 1. What is the unit of energy?
Answer: The standard international unit for measuring energy is the joule. This unit helps us quantify how much energy is being used or transferred.
In simple words: Energy is measured in a unit called the joule.

🎯 Exam Tip: Always specify "SI unit" when asked for the standard unit to be precise.

 

Question 2. Name some simple machines.
Answer: Some examples of simple machines are the pulley, wedge, inclined plane, screw, lever, and wheel and axle. These basic tools help us perform tasks more easily.
In simple words: Pulleys, wedges, and levers are some simple machines.

🎯 Exam Tip: Memorize at least six types of simple machines and one example for each.

 

Question 3. What is a first order lever?
Answer: A first-order lever, also known as a Class I lever, is one where the fulcrum (pivot point) is positioned between the effort (force applied) and the load (object being moved). Common examples include scissors, pliers, and a seesaw.
In simple words: A first-order lever has the pivot point in the middle, between where you push and what you lift.

🎯 Exam Tip: Clearly state the definition and provide examples for each class of lever to score well.

 

Question 4. Lemon juicer belongs to which type of lever? Why?
Answer: A lemon juicer is classified as a Class II lever. In this type of lever, the load (the lemon) is located between the fulcrum (the pivot point) and the effort (where you apply force to squeeze). This arrangement makes it easier to crush the lemon.
In simple words: A lemon juicer is a Class II lever because the lemon (what you press) is in the middle, between the handle (where you push) and the hinge (pivot).

🎯 Exam Tip: When explaining why, make sure to identify the fulcrum, load, and effort positions clearly.

 

Question 5. Define work.
Answer: Work is defined as an action where a force is applied to an object, causing it to move over a distance. Without movement, no work is considered to be done in physics.
In simple words: Work is done when you push or pull something, and it moves.

🎯 Exam Tip: Emphasize that both force and displacement are essential for work to be done in physics.

 

Question 6. Write any three types of energy.
Answer:

• Mechanical energy.
• Thermal energy.
• Chemical energy.

Three common types of energy are mechanical energy, which is related to motion and position; thermal energy, which is heat; and chemical energy, stored in the bonds of molecules.
In simple words: Three kinds of energy are mechanical (like moving things), thermal (heat), and chemical (like in food).

🎯 Exam Tip: Try to include a brief, simple explanation for each type of energy you list.

Try to Answer (Text Book Page No. 104)

 

Question 1. Observe the pictures and put a tick (✓) if work is done and a cross (x) if work is not done.
(i) A farmer plowing a field.
(ii) A person sleeping.
(iii) A person pushing a wall.
(iv) A person drawing water from a well.
(v) A child pushing a stroller.
(vi) An apple falling from a tree.
Answer:
(i) ✓ (Work is done as force is applied and the field is plowed)
(ii) x (Work is not done as there is no movement due to applied force)
(iii) x (Work is not done as the wall does not move)
(iv) ✓ (Work is done as force is applied to lift water)
(v) ✓ (Work is done as force is applied to move the stroller)
(vi) ✓ (Work is done as gravity exerts force and the apple moves)
In simple words: Remember that work happens only when a force makes something move. If nothing moves, no work is done.

🎯 Exam Tip: Work requires both a force and displacement in the direction of the force. If either is missing, no work is done.

Let Us Do (Text Book Page No. 104)

 

Question 1. Mention whether work is done or not in the following activity.

Answer:
In simple words: Work is done when there is movement caused by a force. If there is force but no movement, or movement without force, then no work is done.

🎯 Exam Tip: Always look for both a force being applied and the object moving as a result of that force to determine if work is done.

Try to Answer (Text Book Page No. 109)

 

Question 1. Identify and mention the types of simple machines shown in the pictures.
(i) A picture of an axe.
(ii) A picture of a ramp.
(iii) A picture of children on a seesaw.
(iv) A picture of a valve or steering mechanism.
(v) A picture of a pulley system lifting a weight.
(vi) A picture of a screw or bottle cap.
Answer:
(i) Wedge
(ii) Inclined plane
(iii) Lever
(iv) Wheel and axle
(v) Pulley
(vi) Screw
In simple words: Look at each picture and name the simple machine that it shows. Each tool helps us do work in a special way.

🎯 Exam Tip: Familiarize yourself with common examples of each simple machine type to easily identify them in images.

Let Us Do (Text Book Page No. 109)

 

Question 1. Complete the table by providing examples for each type of simple machine.

Answer:
In simple words: For each simple machine, write down a tool or object that uses that machine's principle to work.

🎯 Exam Tip: Knowing practical examples for each simple machine helps solidify your understanding of how they function in daily life.

Try to Answer (Text Book Page No. 111)

 

Question 1. Name the load, effort, and fulcrum for each lever shown.
Answer:
1. Load
2. Fulcrum
3. Effort
In simple words: When we talk about levers, the load is what you want to move, the effort is where you push or pull, and the fulcrum is the pivot point.

🎯 Exam Tip: Remember the three key parts of any lever: the fulcrum (pivot), the load (what is being moved), and the effort (where the force is applied).

I. Pick Out the Odd One:

 

Question 1. Mechanical energy, Heat energy, Chemical energy, Food
Answer: Food
In simple words: Food is the odd one because mechanical, heat, and chemical are types of energy, but food is just where we get some energy.

🎯 Exam Tip: Distinguish between forms of energy and sources of energy when classifying items.

 

Question 2. Scissors, broomstick, wrench, sea saw
Answer: Broomstick
In simple words: A broomstick is different because scissors, wrenches, and seesaws are all simple machines (levers).

🎯 Exam Tip: Categorize tools based on whether they are simple machines or general implements.

 

Question 3. Petrol, coal, natural gas, water.
Answer: Water
In simple words: Water is different because petrol, coal, and natural gas are fuels that can run out, but water can be reused and replaced.

🎯 Exam Tip: Understand the difference between renewable resources (like water, sun, wind) and non-renewable resources (like fossil fuels).

II. Say True or False:

 

Question 1. Chemical energy is one of the types of lever.
Answer: False
In simple words: This is false because chemical energy is a type of energy, not a type of lever.

🎯 Exam Tip: Be careful not to confuse different scientific concepts like types of energy with types of machines.

 

Question 2. Simple machines usually exchange a larger force to move a heavy object.
Answer: False
In simple words: This is false. Simple machines make work easier by needing less force, not more, though you might have to move the force a longer distance.

🎯 Exam Tip: Simple machines help by reducing the force needed, even if it means applying that force over a greater distance.

 

Question 3. The idea of a simple machine originated with the Greek philosopher Archimedes.
Answer: True
In simple words: This is true. The famous thinker Archimedes was the first to explain how simple machines work.

🎯 Exam Tip: Knowing historical figures associated with scientific discoveries can sometimes be helpful.

 

Question 4. A lever is used to multiply the force.
Answer: True
In simple words: This is true. A lever can make a small push feel like a big push, helping us move heavy things easily.

🎯 Exam Tip: The mechanical advantage of a lever allows it to multiply force, depending on the arrangement of fulcrum, effort, and load.

III. Match the Following:

 

Question 1. Match the following:
1. Class I lever
2. Class II lever
3. Class III lever
4. Wedge
(a) Wheelbarrow
(b) Seesaw
(c) Axe
(d) Hockey stick
Answer:
1. Class I lever - (b) Seesaw
2. Class II lever - (a) Wheelbarrow
3. Class III lever - (d) Hockey stick
4. Wedge - (c) Axe
In simple words: Pair each type of simple machine with its correct example from the list provided.

🎯 Exam Tip: Review examples for each class of lever (Class I, II, III) and other simple machines like wedges to confidently match them.

IV. Choose the Correct Answer:

 

Question 1. second order lever
(a) Scissors
(b) Lemon squeezer
(c) Tongs
Answer: (b) Lemon squeezer
In simple words: A lemon squeezer is a second-order lever because the lemon (load) is in the middle.

🎯 Exam Tip: For Class II levers, the load is always between the fulcrum and the effort.

 

Question 2. Which of the following device converts chemical energy into electrical energy?
(a) Battery
(b) Loud speaker
(c) Solar cell
(d) Electric motor
Answer: (a) Battery
In simple words: A battery changes chemicals inside it into electricity.

🎯 Exam Tip: Batteries are common devices that store energy chemically and release it electrically when needed.

 

Question 3. Which among the following is the non-renewable resources?
(a) Sun
(b) Wind
(c) Water
(d) Petrol
Answer: (d) Petrol
In simple words: Petrol is a non-renewable resource because it comes from very old materials and we cannot make more of it quickly.

🎯 Exam Tip: Non-renewable resources are those that are used up faster than they can be naturally replenished, like fossil fuels.

 

Question 4. SI unit of energy is _________
(a) Joule
(b) kilogram
(c) Mass
(d) Watt
Answer: (a) Joule
In simple words: The correct unit to measure energy is called the Joule.

🎯 Exam Tip: The joule (J) is the standard unit for energy, just as the metre is for length or the second for time.

 

Question 5. A _________ is a push or a pull
(a) Force
(b) Friction
(c) Simple machine
(d) pulley
Answer: (a) Force
In simple words: A push or a pull on something is called a force.

🎯 Exam Tip: Force is the basic concept that describes how objects interact and change motion.

 

Question 6. Simple machines makes work easier by trading _______ for force.
(a) Motion
(b) Work
(c) Friction
(d) Distance
Answer: (b) Work
In simple words: Simple machines help us do tasks more easily by letting us use less force over a longer distance, effectively trading force for movement. They change how we apply force to get a task done.

🎯 Exam Tip: Remember that simple machines change the amount or direction of force, but they do not reduce the total work done.

 

Question 7. A force can cause an object to change its
(a) Shape
(b) Speed
(c) Direction
(d) All of the options
Answer: (d) All of the options
In simple words: When you push or pull something, you can make it change its form, go faster or slower, or move in a different way. A force has many ways it can affect an object.

🎯 Exam Tip: Think of everyday examples like kicking a ball (changes speed and direction) or squeezing a sponge (changes shape) to remember the effects of force.

 

V. Fill in the blanks :

 

Question 1. A _______ should act on an object.
Answer: Water
In simple words: For something to happen to an object, like it moving or changing, water needs to act on it. Water can make things move or change.

🎯 Exam Tip: When filling in blanks, always consider the context of the sentence and what type of physical interaction is being described.

 

Question 2. A pulley is a machine made up of a _______.
Answer: Wheel
In simple words: A pulley is a simple tool that uses a wheel with a rope or cable around it. The wheel helps to lift heavy things more easily.

🎯 Exam Tip: Remember the key parts of simple machines; for a pulley, the wheel is essential for guiding the rope and changing force direction.

 

Question 3. _______ is used to split materials.
Answer: Wedge
In simple words: A wedge is a simple tool, shaped like a triangle, that helps to push two things apart or to split materials. It uses a small force over a large area to create a big splitting force.

🎯 Exam Tip: Understand that a wedge is essentially two inclined planes joined together, which makes it effective for splitting or fastening.

 

Question 4. The screw is used to raise _______.
Answer: Weights
In simple words: A screw helps us lift heavy objects or hold things tightly together. It works like a ramp wrapped around a pole.

🎯 Exam Tip: Recall that a screw is a type of inclined plane, which allows a small rotational force to create a large linear force for lifting or fastening.

 

Question 5. The _______ and sharpener are held together by screw.
Answer: Blade
In simple words: In a sharpener, the blade is held in place by a screw. The screw makes sure the blade stays firm and sharpens correctly.

🎯 Exam Tip: Recognize how screws are used in many tools to join parts securely, like holding a blade in a sharpener or a corkscrew in a bottle.

 

VI. Answer the following questions in one or two sentences :

 

Question 1. What is non-renewable resources?
Answer: Non-renewable resources are resources that cannot be easily replaced once they are used up. Examples include petrol, coal, and natural gas, which take millions of years to form.
In simple words: These are resources that we use faster than nature can make them again. Once they are gone, they are gone forever.

🎯 Exam Tip: When defining non-renewable resources, always mention their finite nature and give common examples like fossil fuels.

 

Question 2. Write about Renewable resources.
Answer: Renewable sources of energy are those that are replaced naturally over time. We can keep using these resources for a long time, like sunlight, wind, and water.
In simple words: These are resources that nature keeps making more of, so we don't run out. We can use them again and again.

🎯 Exam Tip: Focus on the "naturally replaced" aspect for renewable resources and provide clear examples such as solar or wind energy.

 

Question 3. Write the two main conditions are needed for work to be done?
Answer: Two main conditions are needed for work to be done:
1. A force should act on an object.
2. The object should move from one place to another. Both conditions must be met for work to technically occur in physics.
In simple words: First, you need to push or pull something. Second, that thing has to actually move because of your push or pull.

🎯 Exam Tip: Always remember both conditions: application of force AND displacement in the direction of the force. If one is missing, no work is done.

 

Question 4. What is work?
Answer: Work is an action where someone uses a force to move an object. It means energy is transferred to move something over a distance.
In simple words: Work is when you push or pull something, and it moves because of that push or pull.

🎯 Exam Tip: Define work by linking force and motion; specifically, a force causing displacement is the core idea.

 

Question 5. Define energy?
Answer: Energy is defined as the capacity for doing work. It is the ability to make things happen or cause change.
In simple words: Energy is the power to do things, like moving objects or making light and heat.

🎯 Exam Tip: The most important phrase for defining energy is "the capacity to do work" or "the ability to do work."

 

Question 6. Write the type of energy.
Answer: Some common types of energy include:
• Mechanical energy.
• Thermal energy.
• Chemical energy.
• Electrical energy.
• Non-renewable energy.
• Renewable energy. Energy exists in various forms and can be converted from one type to another.
In simple words: There are many kinds of energy, like the energy of movement, heat, chemicals, and electricity.

🎯 Exam Tip: List at least three distinct types of energy, such as mechanical, thermal, and chemical, to show a broad understanding.

 

Question 7. What is simple machine?
Answer: Simple machines are basic tools that help us make our work easier. They help us by changing the direction or magnitude of a force. Examples include pulleys, wedges, and inclined planes.
In simple words: Simple machines are basic tools like levers or ramps that make jobs easier for us. They help us use less effort to do work.

🎯 Exam Tip: When explaining simple machines, always highlight how they reduce effort or change force direction, and provide at least two examples.

 

Question 8. Differentiate Class I lever and Class II lever.
Answer:

The position of the fulcrum, load, and effort changes how a lever works and which class it belongs to.
In simple words: In a Class I lever, the turning point is in the middle. In a Class II lever, the thing you are lifting is in the middle.

🎯 Exam Tip: To differentiate levers, focus on the relative positions of the fulcrum, load, and effort. Remembering a common example for each class helps solidify the concept.