Archimedes' Principle

What does Archimedes' Principle state?

• The buoyant force is greater than the weight of the object.

• The buoyant force is equal to the weight of the displaced water.

• The object’s weight is less than the water displaced.

• The displaced water has no effect on buoyancy.

Answer explanation

Archimedes' Principle states that the buoyant force on an object submerged in fluid is equal to the weight of the fluid displaced by the object. Therefore, the correct choice is that the buoyant force is equal to the weight of the displaced water.

In the diagram example, before the 5 kg weight enters the water, (a)  

• Water is already displaced.

• No water is displaced.

• The weight causes water to spill im

• The weight floats.

Answer explanation

Before the 5 kg weight enters the water, the water is already displaced due to the presence of the weight. This means that the weight is likely resting on the surface, causing some water to be displaced even before it fully submerges.

What happens to water when an object is submerged?

• It compresses the water.

• It displaces some of the water.

• It sinks to the bottom without displacing water.

• It absorbs water.

Answer explanation

When an object is submerged in water, it displaces some of the water equal to the volume of the object. This is based on Archimedes' principle, which states that the volume of water displaced is equal to the volume of the submerged part of the object.

If an object weighs less than the displaced water, it will…

• sink.

• float.

• dissolve in the water.

• stay suspended.

Answer explanation

An object that weighs less than the water it displaces will float due to buoyancy. This principle states that if the weight of the object is less than the weight of the displaced fluid, it will rise to the surface and float.

Match the following conditions with their outcomes regarding sinking objects.

• The object floats.

• If its weight is more than the water it displaces.

• The object floats.

• If its weight is less than the water it displaces.

• The object sinks.

• If it is less dense than water.

• The object remains suspended.

• If it displaces no water.

Answer explanation

An object sinks if its weight is greater than the weight of the water it displaces. This is due to the principle of buoyancy, where an object will float if it displaces a weight of water equal to or greater than its own weight.

What part of Archimedes’ Principle is essential for designing floating boats?

• Minimising water displacement.

• Maximising water displacement.

• Using denser materials.

• Making the boat flat.

Answer explanation

Maximizing water displacement is crucial for floating boats, as it allows them to displace enough water to counteract their weight, ensuring buoyancy and stability on the water's surface.

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When water is displaced, what force acts on the object in water?

• Frictional force

• Gravitational force

• Buoyant force

• Magnetic force

Answer explanation

When an object is submerged in water, it displaces water, creating an upward force known as the buoyant force. This force counteracts gravity and is responsible for the object's ability to float or sink.

What is the relationship between buoyant force and gravity?

• Buoyant force is weaker than gravity.

• Buoyant force is equal to the weight of the water displaced, which opposes gravity.

• Gravity increases buoyancy.

• Gravity cancels buoyant force.

Answer explanation

Buoyant force is equal to the weight of the water displaced, which opposes gravity. This principle, known as Archimedes' principle, explains how objects float or sink in a fluid.

Why is Archimedes’ Principle important in understanding buoyancy?

• It explains how objects dissolve in water.

• It explains the force causing objects to float or sink.

• It applies only to small objects.

• It applies only to liquids.

Answer explanation

Archimedes' Principle is crucial for understanding buoyancy as it describes the upward force exerted by a fluid, which determines whether an object will float or sink based on its density relative to the fluid.

What is essential for large ships to remain buoyant?

• Increasing their density

• Ensuring they displace more water than their weight

• Filling with solid materials

• Making them as dense as possible

Answer explanation

For large ships to remain buoyant, they must displace more water than their weight. This principle, known as Archimedes' principle, ensures that the upward buoyant force is greater than or equal to the downward gravitational force.