Motion, forces Flashcards
Difference between vector and scalar quantities
Vector quantities have magnitude and direction
Scalar quanties only have magnitude
What is the difference between distance and displacement?
Distance is just how far an object has moved (Scalar so no direction)
Displacement is the distance and direction in a straight line from the start to the end point
Example of distance and displacement
Distance - 30m
Displacement - 5 metres north
If you walk 5m north, then 5m south your displacement is 0 but distance travelled is 10m
Difference between speed and velocity
Speed is how fast your going (30mph) with no reguard of direction
Velocity is speed in a given direction (30mph north)
Scalar Quantities
Speed, distance, mass, time, temperature, energy
Vector quantities
Force, displacement, velocity, weight, acceleration, momentum
Equation for speed and velocity
Speed = distance ÷ time
Velocity = displacement ÷ time
The units will change (velocity) will inculude a direction
What axis is time on
x
What does acceleration mean?
Change in velocity in a certain amount of time
Equation for acceleration
Equation for constant acceleration
A = (v-u) / t
V² - u² = 2 x a x z
A is acceleration Z is distance
What happens to acceleration in a circle?
If an object moves at a constant speed in a circle then it’s velocity is constanly changing even though it’s speed is constant.
How to calculate distance on a velocity time graph
Finding triangles and squares and then adding the area up
What is newtons first law?
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it’ll just carry on moving at the same velocity
What does a resultant force do?
It makes something stop moving, change direction, slow down and speed up
Velocity will stay the same
What is newtons second law?
F = m x a
What does newtons second law tell us?
The acceleration of an object is inversely proportional to the mass of the object
What is the difference between mass and weight?
Mass is the amount of stuff/matter. For any object it’s value will stay the same anywhere in the universe.
Weight is the force acting on an object due to gravity pulling it towards the earth
Direction downwards
Mass is scalar and Weight is vecor
Equations to measure weight
Weight = mass (kg) x gravitaional field strenghth (n/kg)
Investigate the motion of a trollry on a ramp
What does inertia mean?
Inertia is the tendency for motion to remain unchanged
What is newtons third law ?
When two objects interact, the forces they exert on each other are equal and opposite
What is a centripetal force?
A force that acts towards the center of a circle
If an object is travelling in a circle it is constantly changing direction so constantly changing velocity meaing it’s accelerating
Examples of centripetal forcses
Gravity (statlights)
Friction (A car turning)
Tension (holding on to a roundabout)
Stopping distance
And eqaution
The distance covered between the driver first spotting a hazard and the vehicle coming to a stop
Stopping distance = thinking distance + braking distance
What is thinking distance?
Thinking distance is the distance the car travels in the driver’s reaction time (the time between noticing the hazard and applying the brakes)
What is braking distance?
The braking distance is the distance taken to stop once the brakes have been applied
Factor affecting braking distance
- Your speed - the faster your going the longer it takes to stop
- The mass of the car- a car full of people and luggage won’t stop as quick as an empty one
- The condition of the brakes - worn or faulty ones won’t be able to brake with as much force
- How much friction is between your tyres and the road (your more likely to skid on dirty, wet or icy roads)
Factors affecting thinking distance
- Your reaction time - this is increased by tiredness, alcohol, drugs and distractions
- Your speed - the faster you’re going, the further you’ll travel during your reaction time
What does more friction do ?
The more friction there is between the tyre and the road the shorter the stopping distance will be.
Explain dangers of large decelerations and estimate forces
What is momentum?
Equation
A property all moving objects have
So a stationary object has no momentum
mass(kg) x velocity(m/s)
What is the conservation of momentum?
In a closed system, the total momentum before an event is the same as after the event
Describe examples of momentum in collisions
When there is a car crash and lock togrther and carry on moving in the same direction
