Post on 10-Feb-2016
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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 = 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