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Discovering how the weight of an object changes how hard we have to push or pull.
Have you ever wondered why you can toss a tiny pebble into a pond with one finger, but you can't move a giant boulder even if you push with your whole body?
Everything around us has weight. Some things are heavy, like a big bag of dog food or a school bus. Other things are light, like a single leaf or a piece of popcorn. Weight tells us how much 'stuff' is inside an object. When we want to move something, we have to use a push or a pull. The weight of the object decides how hard we have to work!
Quick Check
If you are holding a balloon in one hand and a heavy bowling ball in the other, which one has more weight?
Answer
The bowling ball has more weight because it is heavy.
To move a heavy object, you need a strong push. Imagine trying to move a big treasure chest. You would have to use all your muscles! But to move a light object, like a paper airplane, you only need a gentle push. If you use a tiny push on a heavy object, it might not move at all. We can think of it like this: More Weight = More Force needed to move.
1. Imagine an empty swing. You can push it easily with one hand. 2. Now, imagine your teacher is sitting in the swing. The swing is now much heavier. 3. To make the teacher move as high as the empty swing, you have to push much harder with both hands!
Quick Check
True or False: A heavy box needs a smaller push than a light feather to start moving.
Answer
False. A heavy box needs a much stronger push.
What happens if we give a heavy thing and a light thing the exact same push? Let's say you have a heavy bowling ball and a light tennis ball. If you push them both with the same strength, the light tennis ball will zoom far away. The heavy bowling ball is so heavy that the push doesn't make it go very far. Light things are easier to speed up!
1. Place a small glass marble and a heavy red brick on the floor. 2. Give them both a medium-sized flick with your finger. 3. The marble (light) rolls all the way across the room. 4. The brick (heavy) stays exactly where it is because the flick wasn't strong enough for its weight.
We can use what we know to predict (make a smart guess) about how things move. If we see two toys, we look at their size and weight. A toy truck made of metal is heavier than a toy truck made of empty plastic. If we want them to race, we know we have to push the metal one much harder to keep up!
1. You have two grocery carts. Cart A is empty (light). Cart B is full of heavy water bottles (heavy). 2. If you want to stop both carts at the same time while they are rolling, which one will be harder to stop? 3. Cart B is harder to stop because it is heavy. It takes more force to start it AND more force to stop it!
Which of these objects would be the easiest to move with a tiny push?
If you push a heavy rock and a light leaf with the same strength, which one goes further?
You need to use more muscles to pull a heavy wagon than an empty wagon.
Review Tomorrow
Tomorrow, look around your room. Can you find one thing that is 'heavy' and one thing that is 'light'? Think about which one would need a bigger push to move.
Practice Activity
Try this: Get a crumpled piece of paper and a shoe. Try to blow on both. Which one moves? Why do you think the other one stayed still?