I heard that if a car accelerates from rest, a balloon would move forwards instead of backward. Why is this? Science says it’s because of density, but I don’t get their explanation. It also seems like it’s violating newton’s first law.
In: 8
It actually isn’t violating the first law! The helium balloon is currently suspended in the air in the car. Because the balloon is less dense than the air, Archimedes’ principal states that the air exerts a bouyant force on the balloon equal to the displaced mass of the air. This bouyant force will naturally push it to the top, or least dense, portion of the air.
So there is already an outside force acting on the balloon.
Now, when the car accelerates the air inside the car tries to stay in place due to Newton’s first law. This creates a less dense part of the air towards the front of the car. Archimedes’ pricipal delivers an ourside force on the balloon, pushing it towards the front. When the air returns to its normal state the balloon returns to a resting point.
Latest Answers