Physics - Additional Flashcards
What is velocity?
Speed in a given direction
What does the gradient equal in a distance-time graph?
Speed
What is the flat section in a distance time graph?
What does a straight uphill or downhill section mean?
The steeper the graph….
What do the curves represent?
What does a downhill section mean?
- stationary
- its traveling at a steady speed
- the faster its going
- acceleration or deceleration
- its going back to its starting point
What is acceleration?
How quickly velocity is changing
What makes acceleration change?
A change in direction or a change in speed
What does a gradient mean in a velocity- time graph?
Acceleration
What are flat sections? The steeper the graph... What is uphill? What is downhill? What is the area under a velocity- time graph? What does a curve mean?
- steady speed
- the greater the acceleration or deceleration
- acceleration
- deceleration
- it is equal to the distance traveled in that time period
- a change in acceleration
What happens when you brake?
The velocity reduces and the vehicle decelerates
- the gradient of the line is negative as acceleration is negative
What is speed?
How fast something is going
What is the gravitational force?
The force of attraction between all masses
- it gives everything a weight
What does the gravitational force do on the surface of a planet?
It makes everything accelerate towards the ground
What is the mass?
The amount of stuff in a object
What is weight?
The force of gravity pulling it towards the centre of the earth
What is weight caused by?
The pull of gravity
On different plants will the mass or weight be different?
The weight will be different due to the difference in gravitational field strength
What is weight measured in?
Newtons
What is mass measured in?
Kg
How do you reduce your weight?
Go to the equator as the gravitational force is slightly weaker
What is a resultant force?
A resultant force is the overall force on a point or object
There will always be at least….
Two forces acting upon an objects along any direction
What will decide the motion of the object?
The overall effect of the forces, for example if the accelerating force is bigger than the decelerating force than the object will go forward
What happens if there is a number of forces acting upon a single point?
You can replace them with a single force
What happens when all the forces are balanced?
The object is stationary
Why will the resultant force change the velocity of an object?
The resultant force will change it state of rest or motion therefore change the objects velocity
What does a object need to start moving?
A force
If there is no resultant force than ..
There is no change in velocity
- it will just carry on moving at the same velocity
A resultant force means ..
Acceleration
If there is a non zero resultant force than the object will accelerate in the direction of the force
What happens when a jet plane is taking of?
The thrust force of the engines is greater than the air resistance on it, the greater the resultant force the quicker the take off
What happens when a driver applies the breaks?
The breaking force is greater than the force of the engines
What is a reaction force?
When two objects interact the forces they exert on each other are equal and opposite
What is friction there for?
To slow things down
- opposite direction to movement
To travel at a steady speed what do you need to do?
The driving force needs to balance the frictional force
How do you reduce the drag force in liquids?
Make the object more streamlined
What is most resistance caused by?
Air resistance or drag
Drag force increases as…
Speed increases
Describe how terminal velocity works?
When objects start moving the force of gravity is more than the frictional force so they get faster, as they accelerate and speed increases so does the frictional force, this gradually reduced the accelerating force and it wont accelerate any more, it has reached its terminal velocity
What does terminal velocity depend on?
Shape and area
What is the thinking distance?
The distance the vehicle travels during the drivers reaction time
What is the thinking distance affected by?
How fast your going
Tiredness
Drugs
Alcohol
What is the braking distance?
The distance the car travels under the braking force
What is the breaking distance affected by?
How fast your going
How good your brakes are
How good the tyres are
How much grip you have
What is stopping distance?
Thinking distance+ braking distance
What is elastic potential energy?
Work done to an elastic object is stored as elastic potential energy
How does elastic potential energy work?
When applying a force to an object you may cause it to change shape and stretch
After the force has been removed the stored elastic potential energy is converted into kinetic energy
What is hooks law?
The extension of an elastic object is directly proportional to the force but when the force is great enough this stops working
What is the limit of proportionality?
The maximum force that an object can take and still extend proportionally
What are regenerative brakes?
Rather than converting the kinetic energy into heat energy the brakes put the motor into reverse and the wheels are slowed why the motor rushes backwards
At the same time the motor acts as an electrical generator and converts the kinetic energy to electrical energy
How are cars designed to reduce injury?
Crumple zone
- this increases the impact time and decreases the force produced by a change in momentum
Side impact bars
- help direct the kinetic energy of the crash away from passengers to crumple zones
Air bags
- slow you down gradually and prevent you from hitting hard surfaces
Seat belts
- stretch slightly increasing the time taken for wearer to stop and reduce forces acting on it, kinetic energy is absorbed by the seat belt
What is work?
When a force moves an object through a distance energy us transferred and work is done
Why does energy transfer = work done?
When something is moved something else is providing some sort of effort to move it, the effort needs energy, then it does work and moves the object and transfers the energy it receives into other forms therefore energy transferred = work done
What energy is transferred for work it overcome friction?
Work done to overcome friction is mainly transferred into energy by heating
How do brake pads work?
Brake pads become to hot if brakes are applied for too long, the friction between brakes pads and wheel discs oppose the motion of the wheel
Kinetic energy> heat + sound
What happens when an object is moved up?
It gains gravitational potential energy, the increase in GPE is equal to the work done on it by the lifting force
When an object is moved down, the decrease in GPE is equal to the work done by the force of gravity acting upon it
What is elastic potential energy?
Is the energy stored in an elastic object when work is done on it to change shape
The greater the mass…
The greater its velocity so the more momentum the object has
What is the conservation of momentum?
The momentum before an collision equals the momentum after the collision
