P10 Flashcards
What is the equation of resultant force?
Mass X Acceleration
What is newtons second law
The acceleration of an object is proportional of the resultant on the object, inversly proportionaly to the mass of the object
What is it called when the velocity of an object increases
Acceleration is positive
What is it called when the velocity of an object is decresed
Negative acceleration
Equation of acceleration
Acceleration = force/mass
Eg: object accelerates downwards at a constant acceleration of 10m/s and the weight is 1kg
= force/mass = 10/1 = 10m/s
What is weight measure in
Newtons
What is mass always measured
Kg
Equation of weight
Weight = mass X Gravitational field strength
What happens to an object when dropped in fluid
Friction increases towards the object which makes it slow down as it goes down because of its weight
What is terminal velocity
When an object reaches a constant velocity when the frctional force on it is equal and oppisited to its weight . The resultant force is then zero, so its acceleration is also zero
What is the breaking force depend on
Speed of the vehicle when the brakes are first applied and the mass of the vehicle
How are stopping disrances calculated
Thinking distance and braking distance = thinking + breaking
What is thinking distance
How long the driver reacts or the drivers reaction time
What is breaking distance
The distance travelled by the vehicle during the time the braking force acts
What are the main factors effecting stopping distances
1) tiredness, alcohol or drugs that effect the brain or even some distractions such as phones and more
2) how fast the vehicle is travelling, the further it travels before it stops. This is because the thinking distance and the braking distnace both increase with increased speed
3) road conditions such as wet or icy roads (make them skid)
4) poorly made brakes of vehicles
Equation of momentum
Momentum,p (kg m/s) = mass,m (kg) X velocity,v (m/s)
What is the law lf conservation of momentum
In a closed system, the total movement before an event is equal to the total momentum after the event
(Look 10.4 kerboodle for more info)
What happens to a bowling ball once its crashed into the pins
The ball loses an equal amount of momentum and the ball and the pins exert equal and oppisit forces on eachother when they are in contact but no external forces act on them
(Look at 10.4 and .5 for more)
What is impact time?
Where the impact time is long so that the impact force is reduced with removes more a risk of an injury around your body
What makes impact times longer?
Crumple zones, seatbelts and airbag
What is he equation to show how much impact force can be reduced
Force = mass (kg) X change of velocity (m/s) / time taken (s)
Look more on 10.6
Why are air bags useful
When its used its popped out of the wheel and spreads the force on the upper part of a persons body preventing they hitting anything hard in front of them
Where is safety found in playgrounds?
Most playgrounds are fitted with cushioned surfaces below swings and slide just in case children fall off to reduce the risk of head injury.
Why should cyclist always use helmets when riding
Since there are some foam and cushion on it when a person falls over it increases impact time which means it reduce the impact of it afterwards
What is elasticity?
Where an object changes its shape and it returns to its own original shape such as rubber bands and squash balls
How do you find out the extension of the strip?
Extension of the strip of material or spring at any stage = length at stage - original length
What is hookes law
a law stating that the strain in a solid is proportional to the applied stress within the elastic limit of that solid.
