P2 notes

velocity and distance-time graphs

• speed and velocity are both measured in m/s
• speed= how fast you're going
• velocity must have the direction specified
• speed= distance/time
• gradient=speed
• flat= stationary
• straight line= steady speed
• the steeper the graph, the faster it's going
• downhill sections meanit's going back toward it's starting point
• curves= acceleration/deceleration
• a steepening curve means it's speeding up
• a levelling off curve means it's slowing down

acceleration and velocity-time graphs

• acceleration= how quickly the velocity is changing
• can be a change in speed or a change in direction or both
• acceleration= change in velocity/time taken
• m/s squared
• gradient= acceleration
• flat sections= steady speed
• the steeper graph, the greater the acceleration or deceleration
• uphill= acceleration
• downhill= deceleration
• the area under any section of the graph- the distance travelled in that time interval
• curve= changing acceleration

weight, mass and gravity

• gravity attracts all masses
• anything near a planet or star is attracted to it very strongly
• on the surface of a planet, gravity makes all things accelerate towards the ground
• acceleration is 10m/s squared on earth
• gives everything a weight
• mass= amount of stuff in an object
• will have the same value anywhere in the universe
• weight= caused by the pull of the gravitational force
• weight= force measured in newtons
• mass is not a force
• weight= mass x gravitational field strength

resultant forces

• in most real situations there at least two forces acting on a object along any direction
• the overall effect of these forces will decide the motion of the object
• if you have a number of forces acting at a single point, you can replace them with a single force
• if the forces all act along the same line, the overall effect is found by just adding or subtracting them
• the overall force you get is called the resultant force
• the force of gravity is acting downwards
• causes a reaction force
• only way it can be in balance
• without a reaction force, it would accelerate downwards due to the pull of gravity
• if there is a resultant force acting on an object, then the object will change its state of rest or motion
• causes a change in the object's velocity

forces and acceleration

• if the resultant force on a stationary object is zero, the object will remain stationary
• if there is no resultant force on a moving object it'll just carry on moving at the same velocity
• if there is a non-zero resultant force, then the object will accelerate in the direction of the force
• f= ma or a= f/m
• m= mass in kg
• a= acceleration in m/s squared
• f= the resultant force in N
• when two objects interact, the forces they exert on each other are equal and opposite

frictional force and terminal velocity

• if an object has no force propelling it along it will always show down and stop because of friction
• friction always acts in the opposite direction to movement
• to travel at a steady speed, the driving force needs to balance the frictional forces
• you get…