Physics- P4 Revision

• Acceleration= Change in Velocty/Time,
• Speed= Distance/Time,
• Velocity= Displacment/Time,
• Wight= Mass*Gravitaion Field Strenght,
• Force= Mass*Acceleration,
• Momentum= Mass*Velocity,
• Gravitatinol Potential Energy(GPE)= Maa*Gravitatnol Field Strenght*Height,
• Kinetic Energy= 0.5*Mass*Velocity2,
• Power= Work Done/Power,
• Final Velocity2= (Inital Velocty)2+(2*Acceleration*Distance),
• Moment= Force*Distance from piviot,
• Total Stopping Time= Thinking Distance+Braking Distance,
• Reaction Time= 2*Reaction Distance/10,   (Square root the answer),

Gravitation,
Elastic,
Electric,
KInetic,
Sound,

Light,
U--
Nuclear,
Chemical,
Heat,

Key

Can be stored

Can't be stored

The Principle of Conservation Energy

• Energy cannot be created or destroyed but can be transferred from 1 type to another,
• Another name for energy transferred is work done,

The Principle of Moments

• If the anti-clockwise moment & clock-wise moment are equal, then the trebuchet is balanced,
  

The greater the time to stop the smaller the force felt, this time is often called the collision time.

Examples where increased collision time reduces forces:

• Bending elbows to catch a ball,
• Airbags,
• Vertical Seat Belts,
• Crumple Zones,

Gravity acts toward the center of the earth.

The GPE on the earth is 10N/kg,

The GPE on the moon is 1.6N/kg,

• Speed of Light= 300,000,000m/s,
• Speed of Sound= 330m/s,
• Wind- Gental Breeze- 5m/s,
             Strong Breeze- 12m/s,
• Walking- 4km/h --  1m/s,
• Cycling- 24km/h -- 6m/s,
• Running- 16kh/h -- 4m/s,
• Car in Town- 48km/h -- 12m/s

Newtons 1st Law

A stationary object, with no resultant force, will keep still,
A moving object, with no resultant force, will keep moving at a constant speed,

Newtond 2nd Law

A stationary object, with a resultant force, will start moving,
A moving object, with a resultant force, will speed up/ slow down or change direction,

Newtons 3rd Law

If object A exerts a force on object B, then object B exerts an equal but opposite force on object A,

• Acceleration can mean: Speeding up, Slowing Down or Changing Direction,
• Displacement: Shortest distance between 2 points,
• Mass is the amount there is of something,
• Weight is the amount of force on something,
• Momentum is a vector quantity, meaning it has a direction and a speed,
• Power is the rate at which work is done,
• The turning effect of a force is called a moment,

• Any object needs a force to travel in a circle,
• The eath goes at a constant speed, not a constant velocity,
• The speed may be constant but the velocity changes because it is going in a different direction,

The reluctance of a body to start moving, a force is needed to start something moving.

Mass= Force/ Acceleration.

Example

A lorry of mass 20,000kg traveling at 108km/h braked and stops in 102m.
Calculate: a- Deceleration= -3.75m/s,
                 b- Braking Force= -75,000N,