Mass and weight are not the same thing: the mass of an object will stay the same no matter where it is in the Universe, but weight will not. Mass is the amount of stuff an object has. (This is also a good example of why it is important to do experiments yourself and not to just take someone else’s word for it.) To start understanding why Galileo was right, we need to understand the difference between several physics words that are often jumbled together and confused: mass, weight, speed, velocity, acceleration, and force. This is exactly what Galileo did, showing the world that objects of different masses fall at the same rate. But doing the experiment would show you, besides a great view of Pisa, that in fact, both spheres hit the ground at the same time. Aristotle said so too, and for 1,000 years everyone believed him. If someone showed you two spheres of the same size but with different masses, say 1g and 10kg, and asked which would hit the ground first after being dropped from the Leaning Tower of Pisa, what would you say? If you’re like most people, you would say the 10kg sphere would hit the ground first. Why a hammer and a feather will fall at the same rate on the moon but not on Earth.How mass affects the speed at which objects fall.When something falls through air it experiences air resistance.That a force is mass times acceleration.There’s a difference between speed, velocity and acceleration.There’s a difference between weight and mass.Gravity from the Earth makes things fall by pulling objects toward the ground KEY QUESTION: How does mass affect how fast an object falls?īefore the activity students should know: Air resistance does not depend on the mass of the object. When an object with a bigger surface falls through air, it feels more air resistance. Remember that velocity is a vector with direction and magnitude, therefore changes in any (or both) of those factors will produce an acceleration.Īir resistance: The force air exerts on something moving through it. Finally, a change in the direction of the object’s velocity without changing speed, such as if a car is moving North and turns East still moving, then the car accelerated because the direction of the car’s velocity changed. A negative change means the object is moving slower, the car is going from 40mph to 30 mph. For a positive change in acceleration means that the object is moving faster, a car going from 30 mph to 40 mph. When something accelerates it changes how fast it is going or the direction in which it is moving. “The rollercoaster was moving at 65 mph when Billy got sick” is a measure of speed.Īcceleration: How fast the velocity is changing. “The car was going 65 mph south on I-95” is a measure of velocity. Not to be confused with speed, which is only how fast something is moving. Velocity: A measure of how fast something is going in some specific direction. For example, gravity is a force that represents the pull the Earth has on all objects. It is formally defined as mass times acceleration. If the interaction stops, then there is no force. However, your mass will still be the same.įorce: The push or pull an object feels because of interactions with other objects. This means that your weight on the moon will be 1/6 of that on Earth (gravity on the moon is 0.166 times of that on Earth). Weight: Mass (amount of stuff) times how hard the planet is pulling on it (gravity). Mass only says how much actual stuff there is, not how big an object is or how hard something is pulling on it. Not to be confused with weight or volume. Mass: A measure of the amount of stuff (or matter) an object has. Students will use both their eyes and their ears to figure out how mass affects the speed at which something falls.įor more information and ideas on how to implement the activity in your classroom check out the video. This experiment will help students explore those factors, such as gravity and air. There are other factors besides weight that affect the speed of an object as it falls. And why wouldn’t you? After all, rocks fall faster than feathers. If someone drops two objects from the same height, one heavy, one light, which one will hit the ground first? If you are like most people, you may instinctively pick the heavier object.
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