Mass Force and Gravity - Physics - Lecture Slides, Slides of Physics

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Mass, Weight, Force and

Gravity

Mass

• Why is mass topical at the

moment?

• What is the big news in

science?

Mass

• Mass – Amount of stuff (atoms/molecules) in an object. Measured in kg.
• Note: this is pretty much how we use the term weight in common language but that is incorrect.

Weight

Weight – Measures the gravitational pull on something. Measured in N (newtons ). Weight is a measure of force.

What is a force?

Newton's Second Law of

Motion:

• Force is a product of mass and acceleration described by the equation:
• F = ma where f = force, m=mass and a= acceleration

How can we calculate weight?

• We can use an equation we already know to help us:
• g ( gravitational field strength ) = force / mass
• If Force = Weight
• Weight = Mass x g ( gravitational field strength )
• Memorise: W = m X g
• On earth g = 9.8m/s/s Docsity.com

This might help you remember:

Gravity

• The force of attraction between masses. Gravity is the force that makes objects fall to the ground.
• Gravity is actually a very weak force and only very massive objects have significant gravity.
• The force of gravity drops of by the inverse square of the distance (1/ d^2) i.e. if you double the distance the force drops to a quarter.

• Earths Gravitational Field Strength – 9,8N/kg. (The gravitational field strength at the surface of the Earth produces a force of 9.8 N on every mass of 1 kg)

Gravitational field

Earth’s gravitational force makes the ball move down towards the centre of the Earth.

Sun’s gravitational force makes the Earth move in an orbit around the Sun.