🧪 Understanding Upthrust – Through a Story
📖 A Floaty Surprise – Rohan at the River
It was a hot summer day when Rohan and his cousin went swimming in a nearby river. As he stepped into the water, Rohan noticed something strange—when he tried to sit down in the river, **he felt a force pushing him upward!**
“Why is it so hard to stay down?” he asked. His cousin laughed, “That’s **upthrust**, Rohan! Water pushes us up.”
Curious, Rohan threw a stone into the water. It sank. Then he placed a plastic bottle in the river—it floated! His cousin explained, “Water pushes up on everything placed in it. This force is called **upthrust or buoyant force**. Whether things float or sink depends on **how strong the upthrust is compared to the object’s weight**.”
Rohan smiled. Science was fun in the water too!
🎯 Let's Solve Some Puzzles on Upthrust
1. What is upthrust?
Upthrust is the upward force exerted by a fluid on an object placed in it.
2. What causes upthrust?
Upthrust is caused by the pressure difference between the top and bottom of the object submerged in the fluid.
3. A plastic bottle floats, but a stone sinks. Why?
The upthrust on the plastic bottle is greater than its weight, so it floats. The stone’s weight is more than the upthrust, so it sinks.
4. Which force helps a boat float?
Upthrust or buoyant force.
5. True or False: Upthrust acts in the downward direction.
False. Upthrust always acts in the upward direction.
6. If an object floats in water, what can we say about its weight and upthrust?
Its weight is equal or less than the upthrust.
7. Does upthrust depend on the type of fluid?
Yes. Denser fluids (like oil) give more upthrust than lighter fluids (like air).
8. What is another name for upthrust?
Buoyant force
