Section 1: Motion, Forces & Conservation of Energy Flashcards
What is a scalar quantity?
A quantity that only has a magnitude but no direction
What is a vector quantity?
A quantity that has a magnitude and a direction
What are examples of scalar quantities?
Speed
Mass
Distance
Energy
What are examples of vector quantities?
Velocity
Displacement
Weight
Force
Acceleration
Momentum
What is distance?
How far an object has moved (not including its direction)
SCALAR
What is displacement?
The distance and direction in a straight line from an objects starting point to its finishing point
VECTOR
What is speed?
How fast your going with no regard to direction
SCALAR
What is velocity?
Speed in a certain direction
VECTOR
What is acceleration?
The change in velocity in a certain amount of time
What is the acceleration of an object due to gravity close to Earths surface?
10m/s^2
What is the typical speed (m/s) of walking?
1.4 m/s
What is the typical speed (m/s) of running?
3 m/s
What is the typical speed (m/s) of cycling?
5.5 m/s
What is the typical speed (m/s) of a car in a built up area?
13 m/s
What is the typical speed (m/s) of a car on a motorway?
31 m/s
What is the typical speed (m/s) of a train?
Up to 55 m/s
What is the typical speed (m/s) of a plane?
250 m/s
What is the typical speed (m/s) of wind?
5 - 20 m/s
What is the typical speed (m/s) of sound?
340 m/s
What does a flat line show on a distance time graph?
The object is stationary
What does a steepening curve show on a distance time graph?
Object is accelerating
What does a straight line show on a velocity time graph?
Object is travelling at a steady speed
What does a curve that’s levelling off show on a distance time graph?
Deceleration
What is deceleration?
Negative acceleration - shows an object is slowing down
What does a gradient show on a distance time graph?
Speed
How to calculate gradient?
Rise/run
What does a flat line show on a velocity time graph?
The object is travelling at a steady speed
What does an uphill straight line show on a velocity time graph?
There is a constant acceleration
What does a steepening curve show on a velocity time graph?
Increasing acceleration
What does a downhill straight line show on a velocity time graph?
A constant deceleration
What does a gradient show on a velocity time graph?
Acceleration
What does the area under the graph show on a velocity time graph?
Distance travelled in that given time
What is Newton’s first law?
An object remains in the same state of motion unless a resultant force acts on it. If the resultant force on an object is zero, this means:
a stationary object stays stationary
a moving object continues to move at the same velocity (at the same speed and in the same direction)
What is Newton’s second law?
Force = mass x acceleration
What is Newton’s third law?
If object A exerts a force on object B, object B will exert the same force in the opposite direction onto object A
What happens when a girl pushes on a wall (relate to Newton’s third law)?
The wall will push back on the girl with equal and opposite force
What is weight?
The force due to gravity
What is weight caused by near Earth?
The gravitational field around Earth
What does object weight depend on?
Strength of gravitational field at the objects location
What is inertial mass?
The measure of how hard it is to change an objects velocity due to its mass
It’s the ratio of force over acceleration: mass = force/acceleration
What happens to velocity when an object travels in a circular motion with constant speed?
Has a constantly changing velocity BECAUSE direction constantly changes too
What does a changing velocity mean?
The object is accelerating so there’s a resultant force acting on it
What is the force called that’s produced by a circular motion?
Centripetal force - acts towards the centre of the circle
What is the correlation between the mass and momentum of an object?
The greater an objects mass, the greater its momentum
What is the correlation between the velocity and momentum of an object?
The greater an objects velocity, the greater its momentum
What is conservation of momentum?
In a closed system, total momentum before an event equals total momentum after an event
How can Newton’s third law be linked with momentum (use example of two balls)?
- Ball A collides with ball B
- Ball A and ball B exert equal and opposite forces on eachother due to Newton’s third law
- Due to f=ma, ball A decelerates at the same rate that ball B accelerates
- The time the force is applied is the same for both balls, so their change in speed is the same
- Momentum is lost by ball A equals momentum gained by ball B. So total momentum before equals total momentum after
What is the typical human reaction time?
0.2 - 0.9 s