# Force, Motion and Energy

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- Created by: JessicaGrey
- Created on: 25-04-16 16:16

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- Forces, Motion and Energy
- Resultant Forces- "overall force"
- E.g Car engine moving car left. Air resistance moving right. The difference = resultant force
- Resultant force not 0= accelerating or decelerating
- Resultant force 0 = stationary or steady speed

- Distance Time Graphs
- Steeper gradient= faster speed
- Flat line (no gradient) = stationary
- Calculating speed from distance time graph (2 methods)
- Speed= distance / time
- eg 10m in 20 secs. Speed = 10/20. Speed = 0.5 m/s
- Units of speed = m/s

- Gradient method. Difference in y / difference in x

- Speed= distance / time

- Velocity Time Graphs
- Acceleration = (final velocity - initial velocity)/time
- acceleration = m/s^(2)
- eg A car goes from rest to 30m/s in 5 seconds
- (30-0)/5 = 6m/s^(2)

- Analyzing graph
- Steeper gradient = greater acceleration
- Flat line= steady velocity
- Negative gradient= deceleration

- Calculating acceleration from velocity time graphs;
- Difference in y/ difference in x

- Calculating distance travelled
- Area bellow the graph. Units in m

- Acceleration = (final velocity - initial velocity)/time
- Calculating Acceleration: (2 formulas- pick most suitable)
- Acceleration= (final velocity-initial velocity)/time
- Acceleration= Force (resultant force)/mass

- Terminal Velocity
- When speed increases, air resistance increases.
- 1) Person falls out of plane. The force of weight (mass x gravity) is greater than the force of air resistance. = acceleration towards earth
- 2) As speed increases, air resistance increases. till forces are balanced= steady speed= TERMINAL VELOCITY
- 3) Parachute opens. Person slows down (decelerates) because air resistance increases
- 4) Forces Balance eventually= TERMINAL VELOCITY

- 3) Parachute opens. Person slows down (decelerates) because air resistance increases

- 2) As speed increases, air resistance increases. till forces are balanced= steady speed= TERMINAL VELOCITY

- Forces on Elastic Objects
- Work done= Energy Transferred
- Hookes Law simplified "The more force applied, the more and elastic object will stretch provided you do not pass the limit of proportionality"
- Force= Spring constant x extension
- Force=( N). Spring constant =(N/m). Extension= (m)

- Force= Spring constant x extension

- Resultant Forces- "overall force"

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