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