Floating and Sinking

Which word best describes the force from a liquid acting on a floating object?

• Weight

• Upthrust

• Water resistance

• Friction

When an object is floating in water, the object's weight and the upthrust of the water are ________ .

• balanced

• unbalanced

• zero

• dependent on other things

Objects in water feel _______ than in the air.

Hint: think of the upthrust in water compared to the upthrust in air and then the resultant force

• the same

• heavier

• 'weightless'

• lighter

Bobby's blue bowling ball weighs 70N. Bobby puts his bowling ball in jelly (upthrust = 0.064N), will the bowling float or sink?

• Float

• Sink

Select all the forces acting on a pair of glasses sinking in water.

• Weight of the glasses

• Air resistance

• Upthrust

• Explosions

• Light diffraction

Salty water has a _________ density compared to freshwater.

• lower

• similar

• higher

Density means ...

• it is heavy

• the amount of mass an object has, relative to its volume

• you can not see through it

• it can disappear

If the weight of a fizzy drink can is 3.7N, and the resultant downward force in water is 3.5N, what is the size of the upthrust acting on the can?

• 0.2 N

• 7.2 N

• 3.6 N

• 0 N

Why can someone float in the Dead Sea but not in a swimming pool (without using inflatables!) ?

• A big mystery

• The density of the Dead Sea water is greater than for normal water and is high enough to keep a person floating

• The density of the Dead Sea water is lower than normal water and low enough to keep a person floating

• Swimming pool water is usually at 500°C and so is less dense than water in the Dead Sea

If the air in a balloon heats up, making the balloon bigger but still the same mass, what has happened to its density?

• Less likely to pop!

• No change

• Decreased

• Increased