A Baffling Balloon Behavior - Smarter Every Day 113

Helium balloon in an accelerating car.

 

Pulling a Cloth From Under a Beaker

A beaker is placed on top of a cloth, on top of a stool. The cloth is pulled quickly from underneath the beaker, while the beaker remains stationary. The impulse of the net force is made very small by reducing the time over which the cloth acts on the beaker. In other words, the force of the cloth does not act on the beaker long enough to accelerate it, so it does not move.

 

Plate Sliding Under a Soda Can

A can is placed on top of a metal sheet on a stool. A broom hits the sheet causing it to fly from underneath the can, while the can remains stationary. The impulse of the net force is made very small by reducing the time over which the metal sheet acts on the can. In other words, the force of the sheet does not act on the can long enough to accelerate it, so it does not move.

 

Balloons and acceleration

The red balloon is filled with air and is attached to the top of the box, the white balloon is filled  with helium is attached to the bottom of the box.

 As the box is accelerated, ballons move in opposite directions.

 

Hewitt-Drew-it! 19. Newton's Second Law

A video of Paul in the classroom is followed up with a discussion of force, mass, and the acceleration of freely-falling rocks.

Other Hewitt-Drew-it! videos

Misconceptions About Falling Objects - ABC Catalyst

A basketball and a 5 kg ball: which one will hit the ground first?
This is a remake of this video.

Other Veritasium videos

 

Hewitt-Drew-it! 17.Mass/Weight

Paul distinguishes between mass and weight in a video from his classroom, then breaks strings attached to a ball in ways that clarify the distinction.

Other Hewitt-Drew-it! videos

Hewitt-Drew-it! 16.Newton's Laws of Motion

Paul enlists Nellie Newton to illustrate Newton's three laws of motion.

Other Hewitt-Drew-it! videos

Why Does The Earth Spin?

The Earth spins on its axis, completing a full revolution every day. By why does it do this? One of the most common misconceptions in physics is the belief that constant motion requires a constant force. So many people believe there must be some force in the Earth (e.g. gravity, centrifugal force) that keeps it spinning. In truth, no force is required because a fundamental property of mass is that it maintains its state of motion in the absence of external forces. This property is called inertia.

 Other Veritasium videos

Frames of Reference

A nice movie from the sixties made by the "Physical Science Study Committee" (PSCC) series on the laws of physics, inertia, and special relativity in different frames of reference.

Mass - Sixty Symbols

What is mass and where does it come from?

Other Sixty Symbols videos

Egg Experiment to Demonstrate Inertia

If you spin a raw egg and then stop it, it will start spinning again without you having to touch it. A boiled egg, on the other hand, stops and stays stopped. Why is this? Well a raw egg contains a yolk that moves inside the egg independently of the shell. If you stop the shell, the yolk inside continues to move due to its inertia and it therefore gets the egg spinning again.

Other Veritasium videos

The Difference Between Mass and Weight

There is a common perception that weight and mass are basically the same thing. This video aims to tease out the difference between mass and weight by asking people what makes a car difficult to push. The standard answer is that it is difficult to push because it's heavy. But heaviness is a measure of weight, the gravitational pull of the Earth attracting the car to Earth's center. When the car is pushed on a flat road, the force of gravity does not oppose the motion. Instead the resistance felt is an indication of the car's mass which determines its inertia. Inertia is the property of matter that means it tends to resist acceleration - the greater the mass, the less the acceleration for a given amount of force.

Other Veritasium videos

The Law of Inertia: Newton's First Law

This NASA video segment explores how Newton's first law of motion applies to aerospace. An instructor at NASA's National Test Pilot School defines the law of inertia and then explains how the seatbelt in a jet provides an outside force to stop the inertia of the pilot. The instructor also discusses inertia experienced by humans while riding in the test vehicles for space travel.

Centrifugal or centripetal?

A passenger in a frictionless (!) turning cart slides outward. If an observer is looking from the moving cart, he thinks that a centrigual force pushes the passenger outward. But according to an observer at rest, the passenger moves in a straigth line at constant speed (while the cart is turning beneath him). An inward force of friction accelerates the cart toward center of the circle (centripetal acceleration); without this centripetal force, the passenger can't turn and continue in straight line because of its inertia.

Other animations by Yves Pelletier

Eureka! Episode 2 - Mass

Inertia increases with mass.

Other Eureka episodes

MIT Physics Demo -- Wooden Block Between Two Strings

A block of wood is attached vertically between two strings. When the bottom string is pulled slowly, the top string breaks. When the bottom string is pulled quickly, it itself breaks.


See other MIT physics demos

Eureka! Episode 1 - Inertia

Other Eureka episodes

Inertia (card and coin)

Inertia demo (knife and bottle)