Physics P2 Forces and their effects
- Created by: Dominic Hayward
- Created on: 13-05-13 17:24
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- Forces and their effects
- Resultant Forces
- A stationary object remains stationary if the sum of the forces acting on it is zero.
- If an object has multiple forces acting on it-then the resultant force is ALL forces added together.
- When forces are balanced then the resultant force is zero and would mean that...
- A stationary object remains stationary
- A moving object keeps on moving at the same speed and in the same direction
- Non-zero resultant forces
- When the forces are balanced the resultant force is not zero
- This means that a stationary object accelerates in the direction of the resultant force
- Effects of a non-resultant force
- The object was already moving so moves faster than before
- The object is still but begins to move upwards
- The bar was de-celerating so de-celerates faster.
- When the forces are balanced the resultant force is not zero
- Force,Mass and acceleration
- An object will accelerate in the direction of the resultant force. A force on a large mass will accelerate the object less. doubling mass halves mass
- Acceleration= force/ mass
- Forces and Motion
- Distance time graphs
- When going across the objectis stationary
- Gradient= speed
- Speed= distance/time
- Velocity time graph
- Velocity is speed in a particular direction
- Different velocities (eg 2 cars)
- Different speed in the same direction
- Same speed but different directions
- Different speeds in different directions
- Across the graph is constant velocity
- gradient= area under graph
- Acceleration
- a=(v-u)/t (a= acceleration, v+ the final velocity, u=starting velocity and t is time)
- Distance time graphs
- Forces and Braking
- The stopping distance on a car depends on 2 things- thinking distance and braking distance.
- When a vehicle is travelling at a steady speed the engines force is balanced by air resistance.
- Potential forces
- The driving force- from the engine
- Reaction force on wheels- moves the car up
- Friction- between roads and tyres
- Gravity- downward force
- Air resistance- slows down the object
- For something to slow down two things have to occur
- The resistive forces must be increased
- The driving force must be reduced
- Stopping distance= thinking distance + braking distance
- Thinking distance is the distance for a driver to brake.
- This could be increased by tiredness, distractions, alcohol , drugs
- Braking distance is the time taken to stop
- This could be increased by poor brakes, weather conditions
- Forces and terminal velocity
- Falling objects have two main forces acting on them: the weight and air resistance
- The 3 stages of falling. At the start, the object accelerates downwards due to weight
- Then air resistance increases
- Then the objects weight is equalled by air resistance- its terminal velocity
- Then air resistance increases
- Weight is the force acting on an onject- a result on gravity
- W=m*g
- Forces and elasticity
- A force acting on an object can change the shape of an object
- Hookes law- the length of a spring is directly proportional to the force applied
- F=k*e (f is force, k is a spring constant and e is extension
- However, all elastic objects have a different elastic limit
- Resultant Forces
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