Edexcel Physics Topic 1 & 2 (Topic 2 (When an object is moving in…
Edexcel Physics Topic 1 & 2
Topic 1- Key concepts
The SI base units are the metre for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance.
Vector and Scalar Quantities
A scalar quantity has a magnitude but no direction whereas a vector quantity has a direction AND a magnitude. Eg, velocity is speed in a stated direction meaning speed is the scalar quantity of velocity.
Examples of scalar quantities-
Examples of vector quantities-
uniform acceleration= 2 x a x d= x^2 - u^2
Acceleration in freefall is 10m/s^2
The distance travelled is the area between the time axis and the graph line
If the line is straight then the object is accelerating at a constant rate and the same if the line is straight coming down- it is decelerating at a constant rate.
The gradient is equal to the acceleration (for uniform acceleration only)
If the line is horizontal then the object is stationary or travelling at a constant speed
Typical speeds for everyday experiences:
Running- 3 m/s
Cycling- 5.5 m/s
Walking- 1.4 m/s
Cars in urban areas- 13 m/s
Cars on the motorway- 31 m/s
Trains- 55 m/s
Wind- 5-20 m/s
Speed of sound in air- 340 m/s
Newton's First Law:
When the resultant force on a body is zero then the body is moving at a constant velocity or is at rest.
Where the resultant force on a body is not zero then the speed and/or direction of the body is changing.
Newton's Second Law:
f=ma and can be substituted into F= (mv-mu)/t
Weight is measured using a newton meter in newtons. Weight is the force acting on a body due to gravity. The higher gravity, the more the body weighs.
The equation for weight is w=mg
When an object is moving in circular motion, the velocity is constantly changing due to the change in direction even if it is moving at a constant speed
When an object is moving in circular motion there has to be a resultant force which is known as the centripetal force that acts towards the centre of the circle
Inertial mass is the measure of how difficult it is to change the velocity of object. It is defined as the ratio of force over acceleration
Newton's Third Law states that when two objects interact, the forces they exert on each other are equal and opposite.
Momentum is a property of all moving objects, the greater the mass of an object is the greater the velocity, the greater the momentum. Its equation is p=mv
The stopping distance of a vehicle is the thinking distance and braking distance combined
Multiple things can affect the stopping distance including:
the mass of the vehicle
the speed of the vehicle
the condition of the brakes
the road conditions
the friction between the road and the tyres
the driver's reaction time
Many things can affect the driver's reaction time;
In a collision, one body exerts force on another- assuming the other body is at res- making it move but due to Newton's Third Law the body that was at rest exerts the same force on the moving body forcing it to slow down. After calculating the original momentum and the momentum of the second body, they are the same demonstrating conservation of momentum