# Forces & Motion

Everything you need to know

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- Created by: Penruddocke
- Created on: 23-12-14 13:54

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- Forces & Motion
- Distance and Velocity Time Graphs
- Distance Time Graphs
- Calculating speed from graph
- Speed=gradient= vertical/horizontal

- 1) Gradient= Speed
- Flats shows stopped
- Steeper part is faster
- curves show acceleration or deacceleration
- curve starting to level off means slowing down

- curves show acceleration or deacceleration

- Steeper part is faster

- Flats shows stopped

- Calculating speed from graph
- Velocity Time Graphs
- Calculating acceleration from a velocity time graph
- Acceleration= gradient= vertical/ horizontal=Answer

- Calculating acceleration from a velocity time graph

- Distance Time Graphs
- Terminal Velocity
- Free- Fallers reach terminal Velocity
- 1.When free falling objects first set off, they have much more force accelerating then resistance slowing them down.
- 2.As the velocity, increase it builds resistance slowing them down
- 3. The acceleration gradually slows down until both acceleration and resistance forces are equal. This is terminal velocity

- Free- Fallers reach terminal Velocity
- Newtons Three Laws of Motion
- First Law
- Law: Balanced forces mean no change in velocity
- As long as all the forces are balanced it stays still

- Second Law
- Law: A resultant Force means acceleration
- If there is an unbalanced force, then the object will accelerate in that direction

- Third law
- If object A exerts a force on object B then object B exerts the exact opposite force on Object A
- Law: Reaction Forces

- Resultant Force
- To work it out use: Force= mass x acceleration

- First Law
- Momentum
- Meaning: Momentum is conserved when no external factors act. The total momentum after is the same as it was before
- Calculating Momentum use: Momentum= Mass x Velocity
- Force causes changes in Momentum
- Formula: Force Acting (N)= Change in Momentum/Time taken for change to happen

- Acceleration
- Speed Formula Speed= Distance/ time
- Only use this formula when speed is constant

- Calculating Acceleration
- Formula: Acceleration= change in velocity/ Time Taken
- Remember: Change in velocity is final velocity minus initial velocity
- Acceleration is how quickly the velocity is chaging

- Speed Formula Speed= Distance/ time
- Turning Forces
- A Moment is the turning effect of a force
- The force on the spanner causes a turning effect or moment on the nut. A larger force would mean a larger momentum

- Formula: Moment= Force x perpendicular distance (m) between line of action and pivot
- The centre of gravity hangs directly below point of suspension

- A Moment is the turning effect of a force
- Principle of Moments
- Question of Balance- Are the moments equal
- The Answer: If an object is balanced then: Total Anticlockwise Moments= Total clockwise moments

- Forces are not always equal across all support
- If a light rode is being supported at both ends, the upward force provided by each support, won't be the same
- And if the Moments are not equal
- If the total anticlockwise moments do not equal the total clockwise moments, there will be a resultant moment

- Question of Balance- Are the moments equal
- Hooke`s Law
- Hooke's Law says that Extension is proportional to force.
- A metal spring will also obey hooke's Law, if two opposite forces are applied to each end.
- Hooke's law stops working when the force is great enough
- A material can return to its original shape after an elastic deformation expect past hooke's Law

- Gravity and the Universe
- Our Solar System is in the Milky Way Galaxy
- Gravity provides the force that causes orbits
- It provides orbits which excist in:
- 1) Any object travelling in a circle is constantly charging direction
- 2) Any orbit is a balance between forward motion and backward motion
- 3)The planets move around the sun in almost a circular orbit.
- 4) Gravity is responsible for all our other planets in our solar system
- The moon orbits the earth. Other planets also have there own moons.
- Artificial Satellites that are made by man and launched into space.
- Comets are small lumps of icy rock orbiting the earth

- 2) Any orbit is a balance between forward motion and backward motion

- 1) Any object travelling in a circle is constantly charging direction

- It provides orbits which excist in:
- The Universe is a large collection of billions of Galaxies

- Orbital Speed
- Gravity decreases as you go further away
- There are different types of orbits:
- 1) Orbits of moons and planets
- 2)Comets orbit with very elliptical orbits
- 3)Comets have much longer than earth as it has to travel the outer edge of the solar system
- 4) Some artificial earth satellites have an orbital period of exactly one day

- Working out the speed of an Orbiting Object
- Step 1: Calculate the speed of an orbit using: Speed= Distance/time
- Step 2:For a circular orbit, the distance travelled is the circumference of the orbit, which to calculate distance= 2 x pie x radius of orbit
- Step 3- So the formula for speed of an orbit is: Orbital speed= (2 x pie x obital radius) / time period

- Step 2:For a circular orbit, the distance travelled is the circumference of the orbit, which to calculate distance= 2 x pie x radius of orbit

- Step 1: Calculate the speed of an orbit using: Speed= Distance/time

- Vectors
- There are loads of different types of force
- Gravity and Weight
- Reaction Force
- Electrostatic Force
- Thrust
- Drag
- Lift

- Friction is always their to slow things down

- There are loads of different types of force

- Distance and Velocity Time Graphs

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