Weight, Force, Mass & Gravity | Forces & Motion | Physics | FuseSchool

Summary

This video explains the key difference between mass and weight, illustrating how mass remains constant, while weight changes depending on gravity. Using examples like a 1 kg bag of sugar, it shows that mass is measured in kilograms, while weight is measured in newtons and is affected by the gravitational field of different planets. On Earth, a 1 kg object weighs 9.8 newtons, but on the Moon, its weight drops significantly due to weaker gravity. The video also highlights Newton's discovery of gravity and how gravity affects objects differently on various celestial bodies, emphasizing that while mass is fixed, weight fluctuates with gravity.

Takeaways

• 😀 Mass is a measure of how much stuff is in an object, while weight is the force of gravity acting on that mass.
• 😀 Kilograms are units of mass, not weight. Weight is measured in newtons, which is a force.
• 😀 To measure weight, a spring balance or force meter is used, and the result is shown in newtons, not kilograms.
• 😀 The equation that links mass and weight is W = mg, where W is weight in newtons, m is mass in kilograms, and g is the acceleration due to gravity (9.8 m/s² on Earth).
• 😀 The weight of an object depends on the gravitational field strength of the planet or moon it is on, but the mass remains unchanged.
• 😀 On Earth, a 1 kg object weighs 9.8 newtons, but on the Moon, due to lower gravity (1.6 m/s²), the same object weighs only 1.6 newtons.
• 😀 On Jupiter, due to higher gravity (25 m/s²), the weight of a 1 kg object would increase to 25 newtons.
• 😀 Mass remains constant regardless of location—whether on Earth, the Moon, or Jupiter—while weight varies with gravity.
• 😀 Weight and mass are often confused in everyday language, but weight refers to force and mass refers to the amount of matter in an object.
• 😀 The gravitational field strength of a planet determines its gravitational pull, with larger planets like Jupiter having a stronger pull, leading to greater weight on their surface.

Q & A

What is the main difference between mass and weight as explained in the script?

Mass is a measure of how much matter is in an object, while weight is the force exerted by gravity on that mass. Mass is constant regardless of location, but weight changes depending on the gravitational pull of the planet or moon.

How do bathroom scales measure weight?

Bathroom scales measure the force of gravity acting on your mass. They actually measure weight in newtons, but they display it in kilograms as a measure of mass.

Why is it incorrect to say an object weighs a certain number of kilograms?

Kilograms are a unit of mass, not weight. Weight is a force and should be measured in newtons, while kilograms refer to the amount of matter in an object.

How does gravity on the Moon differ from gravity on Earth?

Gravity on the Moon is much weaker than on Earth. The acceleration due to gravity on the Moon is 1.6 meters per second squared, compared to 9.8 meters per second squared on Earth.

What is the equation that links mass and weight?

The equation is w = mg, where w is the weight in newtons, m is the mass in kilograms, and g is the acceleration due to gravity (in meters per second squared).

What would happen to an object's weight if it were on Jupiter instead of Earth?

On Jupiter, the weight of an object would increase because Jupiter has a stronger gravitational pull. For example, a 1 kg object would weigh 25 newtons on Jupiter, compared to 9.8 newtons on Earth.

What is the force required to prevent an apple from falling to Earth?

The force required to prevent the apple from falling is equal to the force of gravity acting on it. With an apple mass of 100 grams (0.1 kg) and gravity of 10 meters per second squared, the force is 1 newton.

How does the concept of mass remain consistent despite location, but weight changes?

Mass remains the same regardless of where you are because it represents the amount of matter in an object. However, weight changes depending on the local gravitational field, which varies from planet to planet.

What would my weight be on the Moon and Jupiter if I weigh 56 kilograms on Earth?

On the Moon, you would weigh approximately 89.6 newtons (about 9.2 kilograms in terms of weight), and on Jupiter, you would weigh around 1,400 newtons (about 143 kilograms in weight equivalent).

Why does the script emphasize the difference between mass and weight in everyday language?

The script emphasizes this distinction because many people mistakenly use 'weight' when they mean 'mass'. Understanding the difference helps clarify the concept of gravitational force and how it affects the weight of an object on different planets.