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Explore the different types of forces, including gravitational, electromagnetic, frictional, and strong and weak nuclear forces. Learn about the force of gravity, why objects fall to the ground, and the difference between mass and weight. Discover how these forces apply to our solar system and watch a fascinating video on objects falling in a vacuum.
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Types of Forces • Gravitational • Electromagnetic • Frictional • Strong and Weak Nuclear
Gravitational Forces • Force of attraction between all objects as a result of their masses and distances between them. • The higher the masses and the shorter the distances between two objects, the greater the force of gravity. • The smaller the masses and the larger the distances between two objects, the weaker the force of gravity.
Why things fall to the ground • When we drop an object, the force of gravity is strong because the earth has a large mass and is close by. The object gets pulled to the ground. • Near the Earth’s surface, objects accelerate to the ground at a rate of 9.8 m/s2, regardless of their masses.
The gravitational force of the Earth decreases as you move away from the planet. • Different planets and stars will have different forces of gravity at their surfaces due to their different masses. The bigger the object the greater the force of gravity. • Gravitational forces also explain the Earth’s tides
Mass vs. Weight • Mass is a measure of the quantity of matter in an object. This does not depend on where the object is. • Weight is a measure of the gravitational force acting on an object. This DOES depend on where the object is.
Weight However, weight and mass are different, how come? weight = Fg = mg which is similar to F=ma m - is mass measured in kilograms (kg) g - gravitational field intensity measured in Newtons/kilogram (N/kg); this is also known as acceleration (m/s2). Fg - is the force of gravity measured in Newtons (N)
1 N = 1 kg x m s2 • We know that earths gravitational pull is 9.8 N => 9.8 kg x m = 9.8 m kg s2 x kg s2
Example • What is the gravitational force (weight) of a 60 kg astronaut on the earth’s surface? Intensity of gravitation on earth is 9.8 N/kg F = mg F = 60 kg X 9.8 N/kg F = 588 N
Example • What is the gravitational force (weight) of a 60 kg astronaut on the Moon’s surface? F=mg F= 60 kg X 1.67 N/kg (force of gravity on the Moon) F= 100.2 N
How much do you really weigh??? • Take your weight in kg (pounds/2.2) and calculate how much weight in Newton’s you are on all the planets in our solar system.
Electromagnetic Force • Force of attraction or repulsion between two charged objects or between the poles of two magnets • We already discussed this earlier in the year • Likes repel, opposites attract
Frictional Force • The force that prevents two objects from slipping over each other • Air resistance is also a force of friction • Friction depends on: • The smoothness of the surfaces (the rougher the surfaces the greater the friction) • The pressure between the surfaces (the greater the pressure the greater the friction)
Strong and Weak Nuclear Forces • Act within the nucleus of an atom • Short range forces • Holds the nucleus together
Hippo & Ping Pong Ball In a vacuum, all bodies fall at the same rate. If a hippo and a ping pong ball were dropped from a helicopter in a vacuum (assuming the copter could fly without air), they’d land at the same time. When there’s no air resistance, size and shape don’t matter!
Video of a Vacuum and two objects • https://www.youtube.com/watch?v=8RKAb5accC0 • Question why do both objects fall at the same acceleration?
