# Physics- P2.1,2,3&4

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Calculating Speed

• The SI unit of velocity/ speed is m/s.
• Velocity is the speed given in a direction.

Acceleration

• Accelertaion is the change in velocity ecery second.
• Acceleration cam take on a negative acceleration= deceleration= slowing down.

Motion/ Distance time graphs

• The steeper the gradient of a distance time graph the greater the speed.
• Key Points:
• 1) An object that is at rest is represented by a horizontal line on a DTG.
• 2) The gradient or slope of a DGT equals the speed.

Forces

• Contact- Those which require touch to happen:
• Friction
• Thrust
• Up-thrust
• Water/ air resistance
• Non-Contact- Those which do not require touch to happen:
• Garvity
• Magnetic
• Static electricity
• Forces can be balanced or unbalanced

Newtons Laws

• 1st Law:If the resultant force acting on an object is 0, the object will remain at rset... or at constant velocity.
• 2nd Law: If a resultant force acts on an object with mass (m- kg), the it will experiance an accelertaion.
• When were talking about the effect of gravity on something, we call the force weight.
• 3rd Law:If an object exerts a force (Fa) on another object,B, then object B exerts an equal and opposite force (Fb) on object A.
• In a swimming pool, you push  cvfdr4the water back and then the water pushes you forward.

Stopping Distances

• Thinking distance- the distance travelled in the time taken for the driver to react.
• Breaking distance- the disatnce travelled once breaked.

Hookes Law

• An elastic material is one that will return to its original length when the force applied is taken away.
• A plastic material is one that does not return to is original length once the force has been removed.
• The amount of…

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