P5 (2) Flashcards
Describe the investigation between force and extension on a spring
Measure natural length of the spring with a millimetre ruler clamped to the stand
Take a reading at eye level and add a marker ( thin strip of tape) to the bottom of the spring
Add a mass to the spring and allow it to come to rest
Record the mass and measure the new length
The extension is the change in length
Repeat this process at least 6 times
Plot a force extension graph of your results
How can you tell if the relationship is linear or non-linear with the line of best fit
If the line of best fit is a straight line - linear
If the line of best fit begins to bend - non-linear
What is the difference between distance and displacement
Distance - scalar - how far an object moves - no direction
Displacement - vector - how far an object has move from their original point - has a direction
Describe the factors that can affect the speed in which a person can walk, run or cycle
Age, terrain, fitness and distance travelled
Other than moving objects what also can vary in its speed
The speed of sound and the speed of the wind also vary.
Describe the typical every day speeds for a person : walking, running, cycling. A car, train, plane and sound (in air)
Walking - 1.5 m/s
Running - 3 m/s
Cycling - 6 m/s
Car - 25 m/s
Train - 30 m/s
Plane - 250 m/s
Sound - 330 m/s
What does the speed of sound and wind depend on
Depends on what the sound waves are travelling through
Temperature, atmospheric pressure and if there are any large buildings nearby
Explain how a motion in a circle involves constant speed but changing velocity
As direction is always changing, velocity is changing but speed is not changing
From a distance-time graph, how can the speed of a object be calculated
The speed of an object can be calculated from the gradient of its distance–time graph.
If an object is accelerating, how can speed be determined
If an object is accelerating, its speed at any particular time
can be determined by drawing a tangent and measuring the
gradient of the distance–time graph at that time
On a distance-time graph, how do you find the velocity on a curve
Draw a tangent then work out gradient
What does a flat line on a velocity time graph tell us
Object is moving at constant velocity
What does the gradient of a velocity time graph tell us
Acceleration/Deceleration of an object
How do you work out the distance in a velocity time graph
Straight line : area of strips
Curve: number of squares
When is terminal velocity reached
When resultant force is 0
Weight has the same magnitude as air resistance
What does the size of air resistance depend on
Surface area and velocity
What is newtons first law of motion
A resultant force is required to change the motion of an object
What is newtons second law of motion
When a non-zero resultant force acts on an object, it will accelerate
Size of the resultant force is directly proportional to the acceleration it causes
Describe how the moon is always accelerating although it moves at constant speed
Moves in a circular motion
Direction is always changing
Velocity is changing
Acceleration is changing
Define the term ‘inertia’ and ‘inertial mass’
Tendency for the motion of an object to remain unchanged
How difficult it is to change an objects velocity (mass/acceleration)
What is newtons third law
Whenever two objects interact, the forces they exert on each other are equal and opposite.
What is stopping distance
total distance a car travels from the moment the driver first notices an obstruction
(thinking distance + braking distance)
What is the range for typical reaction time
Describe factors that may increase thinking distance
2-9ms
Drugs
Alcohol
Tiredness
Describe the factors that may increase braking distance
Ice on the road
Worn out brakes
Worn out tyres
If a vehicle drives three times as fast, what happens to breaking distance
Breaking distance increases by 9 times
Which factor increases both thinking and breaking distance
Speed of a vehicle
When does newtons third law not apply
When the two interacting forces are different
Describe the events of someone skydiving
Initially, weight downwards much larger than air resistance upwards (resultant force in a downwards direction) - accelerates towards the ground
As object accelerates and velocity increases, air resistance increases (collides with more air particles)
Until air resistance = weight - no resultant force - terminal velocity reached
Describe the events of someone opening their parachute
Surface area increases massively, collides with more air particles, air resistance increases, resultant force is upwards, decelerate downwards
More they slow down, the lower the air resistance till it equals weight again - no resultant force - new terminal velocity (lower than initial terminal velocity)
What happens when a force is applied to the brakes of a vehicle
Work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increases
As braking force increases what happens and also describe the dangers of large decelerations
The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control
Describe the conservation of momentum
In a closed system, total momentum before the collision = total momentum after the collision
