P3 Flashcards
What are scaler quantities? + Exmaple
Scaler quantities, have a size ( or magnitude ) only
Example : speed of the car was 60 km
What are vector quantities? + example.
Vector quantities, have both size ( magnitude ) and direction
Example : the boat sailed 30 km north
Some examples of scalar quantities?
Speed and distance
Some examples of vector quantities?
Velocity, acceleration and displacement
What is acceleration?
An object acceleration is the rate at which its velocity is changing
What unit is acceleration measured in?
m/s^2
What is the equation for acceleration?
A = (v-u) / t
What is the equation for speed?
S = d / t
What does the gradient of a distance time graph tell me? How do I work it out?
The speed, work it out by diving change in y over change in x
What does the gradient and area under the line tell me in a velocity time graph? How do I work it out?
Gradient = acceleration, by dividing change in y over change in x
Area under the line = distance, by timing the two values together ( depends on shape too )
What is the equation for motion?
V^2 = u^2 + ( 2 x a x d )
What is the equation for kinetic energy?
KE = half ( 1/2 ) x m x v^2
What is a force?
A force is a push or pull
What are forces measured in?
Newtons
What are the different types of forces??
- Contact forces
- Non-contact forces
Name examples of contact forces?
- Friction
- Tension
- Drag / air resistance
- Normal contact force
- Upthrust
Name examples of non-contact forces?
- Magnetism
- Weight ( gravity )
- Electrostatic
Do you know how to draw a free body diagram??
Yes
What are the steps injuring a free body diagram?
- Draw the object as a dot
- draw the forces on the object as arrows to scale as the size of the forces in the direction
How do you calculate the resultant force of two forces at right angles?
You use Pythagoras theorem
What are the rules when calculating resultant forces on a free body diagram?
- Forces that act in the same direction are added
- Forces that act in opposite directions are taken away from each other
What is Newton’s first law?
An object will stay at rest or move with a steady velocity, unless a resultant force acts on it
What is inertia?
Inertia is how hard it is to change the velocity of an object
What is equilibrium?
If the forces on an object are balanced, there is no resultant force and we say the object is in equilibrium
What happens when the forces on an object are unbalanced?
- A stationary object starts to move
- A moving object, changes, speed, or direction
What is the equation for force with other values?
F = m x a
Force = newtons
Mass = kg
Acceleration = m/s^2
Describe the motions at each stage of a skydivers jump in the house he achieves terminal velocity?
- at the start of his jump in the air , air resistance is zero so, he accelerates downwards
- As his speed increases, his air resistance will increase
- Eventually the air resistance equals his weight, the forces are balanced, so his speed becomes constant = terminal velocity
- When he opens his parachute, the air resistance suddenly increases, causing him to slow down
- Because he is slowing down, his air resistance will decrease
- Finally, the air resistance balances his weight. The skydiver has now reached a new lower terminal velocity
What is Newton’s third law?
For every action, there’s an equal and opposite reaction
When shaving terminal velocity, what is weight and air resistance affected by?
- Weight is affected by mass
- Air resistance is affected by surface area and speed
What is work?
When you move something against a resistance force you are doing work
Equation for work done?
W = f x d
Work done = Joules ( J)
Force = Newtons ( N)
Distance = metres (m)
What is momentum and what is it affected by?
Momentum is movement, it is affected by:
- Mass: the larger, the mass of the large is the momentum
- Velocity: the faster, the object moves the larger the momentum
- Directions: momentum, candy, positive, or negative depending on direction
What is the equation for momentum?
P = m x v
( P ) Momentum = Kgm/s
Mass = Kg
Velocity = m/s
What is the law of conservation of momentum?
Momentum is conserved when no external forces act:
Momentum before = momentum after
What is an elastic collision?
A collision in which no energy is transferred to other stores
What is a inelastic collision?
A collision in which energy is transferred to other stores
Explain circular motion?
- an object, moving any circle, changes direction all the time
- This means that its velocity is changing ( even if it’s at a steady speed )
- It is also accelerating ( because of the change in direction)
- It keeps moving because of the centripetal force acting towards the centre of the circle
What is Power?
The amount of energy transferred every second
Equation for power?
P = E / T
Power = Watts ( W )
Energy = Joules ( J )
Time = seconds ( s )
What is hooks law? What does it mean?
The extension of a spring is proportional to the spring up until the limit of proportionality
- This means that when you double the force on his bring the extension doubles as well
What is the equation for force involving spring constant ?
F = K x E
Force = Newtons ( N)
Spring constant = N/m
Extension = m
Equation for elastic potential energy?
E = half ( 1/2 ) x k x e^2
What are some materials that do not stretch proportionally to the force applied to them, do not follow hooks law?
- An elastic band
- Glass
- Copper
What does a force extension graph look like for an elastic band? Why is it abnormal?
- elastic band stretches a different amount for each newtons of force added it does not follow hooks law
What does a force extension graph look like for an glass? Why is it abnormal?
- Glass followers hook slow at first, but it is brittle and breaks easily
What does a force extension graph look like for an Copper? Why is it abnormal?
- at first copper seems to follow hooks law. However, soon it’s start stretching even when there is no more force being added
What is a gravitational field?
An area where a mask feels an attractive force, it is measured in N/kg
What is the relationship between mass and gravitational fields?
Everything that has mass has a gravitational field
For example, the Earth has a strong gravitational field because it has such a large mass
What is the gravitational field strength on Earth?
10N/kg
What is mass?
A measure of how much stuff an object is made of
What is mass measured in?
Kilograms
What is weight?
Wait is the name we give the force due to gravity
What is weight measured in?
Newtons
What is the equation for weight?
W = m x g
Weight = Newtons ( N )
Mass = kilograms ( kg)
Gravitational field strength (p= N/kg
What is the equation for gravitational potential energy?
E = m x g x h
Energy = Joules ( J )
Mass = kilograms ( kg )
Gravitational potential field strength = N/kg
Height = metres ( m )
What is a moment?
A moment is the turning affect of a force
What are the units of a moment?
Nm ( newton metres )
What is the equation for moment?
M = f x d
Moment = newton metres ( Nm )
Force = newtons ( N )
Distance ( metres )
Label the distance-time graph ?
Purple = Fast steady speed
Red = returning to point zero
Green = slowing down / decelerating
Orange = speeding up / accelerating
Label the velocity- time graph?
Red = decelerating
Orange = stationary
Yellow = steady speed / constant speed
Light green = accelerating quickly
Dark green = accelerating slowly
