Grade 6

Elementary

6 min

Lesson 2 of 12

What is Scientific Work?

Not Started

Learning the specific definition of work in physics compared to everyday chores.

Imagine you spend an entire hour pushing against a heavy brick wall with all your might. You're sweating, tired, and your muscles ache—but according to a physicist, you have done exactly zero work. How can that be?

Learning Objectives

1.Define scientific work as a force applied over a specific distance.
2.Distinguish between everyday 'effort' and the scientific definition of 'work'.
3.Identify real-world scenarios where work is being done versus where it is not.

What is Scientific Work?

In our daily lives, we use the word 'work' to describe anything that takes effort, like studying for a test or holding a heavy box. However, in physics, work has a very specific meaning. For work to happen, two things must occur: you must apply a force to an object, and that object must move a certain distance in the direction of that force. If the object doesn't move, no work is done! We calculate work using this formula:

W = F \times d

where

W

is Work,

F

is Force (measured in Newtons), and

d

is Distance (measured in meters).

Let's look at a simple task. You lift a book from the floor to your desk. 1. You apply an upward force of

10\text{ N}

to the book. 2. The book moves upward a distance of

1.5\text{ m}

. 3. Since the book moved in the direction of your force, you did work! 4. Calculation:

W = 10\text{ N} \times 1.5\text{ m} = 15\text{ J}

The unit for work is the Joule (

J

Quick Check

If you push a parked car with $500\text{ N}$ of force but the car does not budge, how much work have you done?

Look at the formula

W = F \times d

. What happens if

d

is zero?

Answer

Zero work. Because the distance ( $d$ ) is 0, the total work ( $W$ ) is also 0.

Direction Matters

It isn't enough for an object to just move; it must move in the same direction as the force you are applying. Imagine you are carrying a heavy tray of food across a cafeteria. You are using an upward force to keep the tray from falling, but you are moving forward across the room. Because the upward force and the forward motion are not in the same direction, your arms are technically doing no scientific work on the tray while you walk!

You push a grocery cart down an aisle. 1. You apply a horizontal force of

20\text{ N}

forward. 2. The cart rolls

10\text{ m}

forward. 3. Because the force and motion are in the same direction, work is done. 4. Calculation:

W = 20\text{ N} \times 10\text{ m} = 200\text{ J}

Quick Check

Which requires more scientific work: Holding a $50\text{ kg}$ weight perfectly still above your head, or lifting a $1\text{ kg}$ feather off the ground?

Remember, no movement means no work!

Answer

Lifting the feather. Holding the weight involves no movement ( $d=0$ ), so no work is done. Lifting the feather involves movement, so work is done.

The Joule: Measuring Energy

When you do work on an object, you are actually transferring energy to it. This is why the unit for work, the Joule ( $J$ ), is the same unit used for energy. One Joule is defined as the amount of work done when a force of $1\text{ Newton}$ moves an object a distance of $1\text{ meter}$ . If you do more work, you are simply using more energy to move something further or push it harder.

Two students, Alex and Sam, both weigh

500\text{ N}

. 1. Alex climbs a flight of stairs that is

3\text{ m}

high. 2. Sam stands at the bottom of the stairs holding a

100\text{ N}

box for 5 minutes. 3. Alex's Work:

W = 500\text{ N} \times 3\text{ m} = 1500\text{ J}

4. Sam's Work:

W = 100\text{ N} \times 0\text{ m} = 0\text{ J}

Even though Sam might feel more tired from holding the box, only Alex performed scientific work because Alex moved a distance.

Key Takeaways

1Scientific work requires both force and movement in the same direction.
2The formula for work is $W = F \times d$ .
3Work is measured in Joules ( $J$ ).
4If there is no displacement (movement), the work done is always zero, regardless of the effort.

Quick Check

Multiple Choice

In which of these scenarios is scientific work being done?

Multiple Choice

If you apply a force of $5\text{ N}$ to move a toy car $4\text{ meters}$ , how much work have you done?

True/False

If you carry a heavy box horizontally across a room, your upward lifting force is doing work on the box.

What's Next?

Review Tomorrow

Tomorrow morning, try to remember the two 'ingredients' required for scientific work to happen.

Practice Activity

Look around your house today. Find three examples of 'effort' that are NOT scientific work, and three examples of actual scientific work.

Browse

Browse

What is Scientific Work?

Learning Objectives

What is Scientific Work?

Direction Matters

The Joule: Measuring Energy

Key Takeaways

Quick Check

What's Next?

What is Scientific Work?

Learning Objectives

What is Scientific Work?

Direction Matters

The Joule: Measuring Energy

Key Takeaways

Quick Check

What's Next?