Topic 2 Motion And Forces Flashcards
What is Newton’s first law?
A body will remain at rest or continue in a straight line at a constant speed as long as the forces acting on it are balanced
What is Newton’s second law?
F= m x a
Force = mass x acceleration
Weight and mass
Weight is the force that a body experiences due to its mass and the size of the gravitational field that it is in.
Mass is a measure of the amount of matter that is contained within a three-dimensional space
Weight= mass x gravitational field strength
W = m x g
The value for earth gravitational field strength is 10N/Kg
Weight is measured in newtons
Momentum and force
Momentum of a moving object depends on its mass and its velocity
Momentum= mass x velocity
P= m x v
Force is the rate of change of momentum
Force= change in momentum/ time
F= (mv - mu)/t
What is Newton’s third law?
Every action has a equal opposite reaction.
Human reaction time
It takes a typical person between 0.20s to 0.25s to react to the stimulus.
However when driving some things might affect reaction time:
- tiredness
- alcohol and drugs
- distractions
- age
What is stopping distance, thinking distance and breaking distance?
Stopping distance is the total distance over which a vehicle comes to rest.
Thinking distance is the distance the car travels while the driver reacts to the danger
Breaking distance is the distance the car travels while it is slowing down
Factors affecting this are:
- tiredness
- distracted
- alcohol and drugs
- icy roads
- tyres are worn down
- mass of the car
Distance time graphs
Straight line up- constant or steady speed
Curving line up- accelerating
Curving line down- decelerating
Straight line across- stationary
How do you determine speed?
You can measure speeds of objects in the lab by using light gates connected to a computer or data logger
Typical day to day life speeds
Walking- 1.5 m/s
Running- 3 m/s
Cycling- 6 m/s
Speed of sound in air- 330 m/s
Gale-force wind- 16 m/s
What is the relationship between the weight of a body and the gravitational field strength?
The weight of a body on the surface of the earth acts inwards towards the earth’s centre
What is circular motion?
A body will move in a circular path if its motion is at right angles to a force that acts inwards along the radius of the path
Core practical force and acceleration
Two light gates
Trolley on a ramp
If u change the mass, the slope or gradient needs to stay the same
The acceleration of the trolley does not depend on the mass of the trolley
