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Acceleration and gravity. Acceleration. Measure of the rate at which an object’s velocity is increasing (or decreasing). Units: metres per second per second (m/s/s or m.s -2 ). Formula: acceleration = change in velocity ÷ change in time a = Δ v/ Δ t. Gravity.
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Acceleration • Measure of the rate at which an object’s velocity is increasing (or decreasing). • Units: metres per second per second (m/s/s or m.s-2). • Formula: acceleration = change in velocity ÷ change in time • a = Δv/Δt
Gravity • Gravity is a force which makes a free falling object accelerate. • On Earth the force of gravity makes at object accelerate at about 10 m.s-2. • This means that the velocity of an object increases by 10ms-1 every second it falls. • It doesn’t matter what the mass of an object is. It falls at the same rate. https://www.youtube.com/watch?v=_mCC-68LyZM • Feather and hammer on the moon: https://www.youtube.com/watch?v=wtsNOMTlS7E
Felix Baumgartner • Felix Baumgartner jumping from the edge of space: https://www.youtube.com/watch?v=dYw4meRWGd4 • An object falling in Earth’s atmosphere will accelerate until an opposing force (air friction or drag) equals the force of gravity. • The maximum speed of a falling object in the atmosphere is called terminal velocity: https://www.youtube.com/watch?v=p0IZsfzDS4s
Force and mass • A force is a push or a pull (a twist is a combination of both). • A force applied to an object in the absence of friction will make the object accelerate. • The larger the force, the greater the acceleration. • The larger the mass of the object, the smaller the acceleration. • Formula: Force = mass x acceleration, F=ma • https://www.youtube.com/watch?v=iwP4heWDhvw
Practical applications • Small car vs Big car: • https://www.youtube.com/watch?v=sxUx6qi0I_k • https://www.youtube.com/watch?v=lTAUV1Yj4NE • https://www.youtube.com/watch?v=GKe6WhFLmi0 • The best two ways to increase acceleration of any object is to decrease mass and increase the force.
Friction • Friction is a force that opposes motion. • Friction converts kinetic energy into heat energy. • Reducing friction increases both acceleration and also the maximum speed an object can travel on Earth. • Remember: Friction is not a factor that needs to be considered with moving objects in space.
Applications of friction reduction • Cycling: https://www.youtube.com/watch?v=-aUOzYAuL48 • The worlds fastest Indian: https://www.youtube.com/watch?v=02Yy1vihIKs