P2 Flashcards
How many seconds in a hour, how many meters in a mile
3,600s = 1h
1609m = 1 mile
How can a force change an object
It can change the shape or the motion. It can accelerate a body.
Forces are represented with Newtons(Vector’
What is newton’s third Law?
When two bodies interact they exert a force on each other , equality in size but opposite in direction
Give an example of a non contact force
Gravitation field, magnetic, electrostatic
A free body diagram shows
The result force
How do you calculate free bodies in the horizontal and vertical plane?
Pythagoras Theorem , but make sure the diagram is tip to head
To find the direction of the pythagora’s Theron :
Find the degree of the angle using trig.
The angle comes off at the new line and thE largest quantity
How would you resolve a force?
You have to find the horizontal and vertical plane of a diagonal line . You would use trigonometry using the angle and the resultant force. Then do two separate equations to find the two separate values.
Or scale diagram
What is Newton’s first law?
A body will remain at rest on continue at uniform velocity unless acted upon by a resultant force
What is inertia ?
How difficult it is to change the velocity of a body.
The greater mass, the greater interia
What is Newton’s second law?
The acceleration experienced by a body is directly proportional to the resultant force
What is the equation of newton’s 2nd Law
F= M A
N= kg m/s**2
What is magnitude?
The size of something
What is the difference between a scalar and a vector quantity ?
A vector has magnitude and direction whereas a scalar quantity only has magnitude
What is acceleration?
The rate of change of velocity.
If direction or speed changes so does acceleration
V - U
———
T
Why is a body moving in a circle at constant speed have a resultant force?
It’s changing direction and therefore velocity, constantly accelerating which means (N’s 1st law) there is a resultant force.
This resultant force is known as centripetal force
What is terminal velocity?
Constant velocity , zero resultant force
Describe a parachuter’s journey
- Weight acts down, no a lot of drag, RF increases down, acceleration, increasing velocity
- Air resistance increases to the point where RF is zero, terminal velocity - no acceleration & constant velocity
- Remains until parachute is opened, SA increases, increasing drag. RF is acting upwards, decreasing velocity
- As velocity decrease so does drag so eventually the RF becomes zero again, terminal velocity 2, contact velocity, zero acceleration
Define momentum
How difficult it is to stop a moving body. The two factors affecting this are mass and velocities.
(A vector value)
How do you calculate momentum? 🅿️
Mass * velocity = momentum
Kg * m/s = kg m/s
What is the law of conservation of momentum?
The total momentum before an event is equal to the total momentum after an event .
How do you apply the LofM when two stationary bodies push and move away from each other?
Eg (explosion)
The total momentum before and after must equal zero , as they were stationary.
To calculate a total:
. Calculate the first object using P = mv
. Then calculate the second object by knowing the fact the Momentum is negative, to equal zero, as they were going in opposite directions
How do you use the L of C when two bodies collide and move off together?
Calculate the total before , by calculating each separate component’s momentum and adding them together.
Calculate the total after but appreciate it as one value , use the momentum of previous to find out other variables
What is work?
The transfer of energy .
Whenever a force acts upon an object, work is done
What is the work equation?
Work done = force * distance
J = N *m
What happens in term of energy when work is done?
Energy is transferred from one form to another.
Eg : kinetic to gravitational potential energy,
When a body is lifted
What is power?
The rate of energy transfer
What is the power equation?
P = E/T
W= J / s
How do you calculate the gravitational force?
Gravitational force = mass * gravitational field strength
N = kg * (N/ kg)
The gravitational field strength is always 10 N/kg on earth
What is the kinetic energy formula?
Kinetic energy = 0.5 ✖️mass ✖️ (speed2)
J =. Kg* (m/s)2
E= 1/2 mc squared
What is the potential energy formula?
Potential energy = mass * height * gravitational field strength
J = kg * m * (N / kg)
U=mgh
What is an elastic body?
Objects that return to their original shape when the deforming force is removed
What is the deforming force?
Stretching , compressing or bending a body to change the shape
What is a plastic body?
Objects that do not return to their original shape when the deforming force is removed
What body is a spring?
Elastic, as they are designed to return to their original position. However if too large of a force is applied they will break.