Forces P1 Flashcards
Types of forces
- non contact (magnetic force)
- contact (reaction force)
- electrostatic force
- friction
- air resistance
- gravitational force
What do opposite charges and like charges do
- opposites attract
- like repel
What is Newton’s first law of motion
- if the resultant force acting on a stationary object is zero then the object will remain stationary
- if the resultant forcing acting on a MOVING object is zero, then the object will continue moving in the same direction at the same speed (with the same velocity)
(An object will stay stationary or continue moving at the same speed and direction, unless a resultant force is applied)
Work done equation
work done (j) = force (n) x distance (d)
What are the types of energy transfer
- mechanical work (a force moving an object through a distance)
- electrical work (charges moving due to a pd)
- heating (due to temp difference caused electrically or by chemical reaction
- radiation (energy transferred as a wave like light (radiation) and infrared (radiation) which are emitted from the sun)
What will happen if we take away the forces acting on elastic materials
- they will always return to their original length or shape
What is elastic deformation
When the elastic changes shape
What is the difference between elastic and in elastic deformation
- elastic deformation is reversed when the force is removed
- inelastic deformation is not fully reversed when the force is removed (there is a permanent change in shape)
What do you have to do in order to change an objects shape or length
Apply more than one force
What would happen if you only applied one force to a stationary object
The forces are no longer balanced, so the object would simply move rather than change shape or length
Example of inelastic materials
- certain polymers
What is the calculation for the force needed to stretch an elastic object OR compression when an elastic object is squeezed
Force (n) = spring constant (n/m) x extension (m) OR compression (m)
F = k x e
What is only true if an object is not inelastically deformed
- when stretching or compressing an elastic object, we’re using a force to do work (elastic potential energy is stored in object)
- work done is equal to the elastic potential energy
What are contact forces and non contact forces
- contact (physically touching)
- non contact (physically separated)
What are examples of a contact force
- Tension in a rope
- friction
- air resistance
- normal contact force (can only happen if the two objects are in direct contact)
Examples of non contact force
- gravitational force
- electrostatic force (the force between two charged objects)
- magnetic force
What do objects with opposite charges experience
An electrostatic force of attraction
What’s the difference between velocity and speed
- velocity has a direction and so is a vector quantity
What is a scalar quantity
When something has magnitude but no direction
What is the speed calculation
speed (m/s) = distance (m) divided by time (s)
In triangle distance is at the top
What does displacement tell us
- The distance that an object moves in a straight line from the start point to the finish point
- it is a vector quantity as it includes the direction and magnitude
What must displacement include
The direction of that straight line
What is speed
A scalar quantity as it does not involve direction
What are the typical speeds
- normal walking speed = 1.5m/s
- running speed= 3m/s
- cycling speed= 6m/s
- car on a main road= 13m/s
- fast train in the uk= 50m/s
- cruising aeroplane= 250m/s
What does speed depend on
- age
- fitness (whether they were fitter or unfit)
- the terrain (uphill would be slower and flatter would be faster)
- distance travelled
What is the typical value of speed of sound in air
- 330m/s but the speed in air can vary depending on the weather (speed travels faster on warmer days rather than colder days)
Speed of a moving object…
The speed of a moving object is rarely constant
Distance travelled by an object moving at a constant speed (average speed) calculation
Distance (m) = speed (m/s) x time (s)
What is velocity
- A vector quantity
- it includes both magnitude and direction
- it’s an objects speed in any direction
How is velocity calculated
The same way as speed, just state the direction they are going in
What happens to the velocity of an object if it’s moving at a constant speed in a circle
The velocity is constantly changing even though it’s speed stays constant
How can an object moving along a straight line be presented in terms of distance
A distance time graph
How do you work out the speed on a distance time graph
Using the gradient which is,
distance travelled divided by time taken
What does an upwards curve on a distance time graph mean
The object is constantly increasing in speed (accelerating)
What does the acceleration tell us
The change in it’s velocity over a given time
Calculation for acceleration
Change in velocity (m/s)
————————————- = acceleration (m/s2)
Time (s)
Change in velocity is at the top of triangle
What do you do if the velocity in a question reduces (acceleration)
Take it away, if it was reduces to zero from 6 you would do 0-6=-6
What do you have if you end up with a negative number in a question (acceleration)
- the object is slowing down and decelerating
- deceleration
What does the gradient of a velocity time graph tell us
The acceleration of the object
What does it mean if the line is horizontal on a velocity time graph
The object is travelling at a constant speed
What is the calculation for acceleration on a velocity time graph
Final velocity (m/s) - initial velocity (m/s)
——————————————————-
Time (s)
=
Acceleration (m/s squared)What does the total area under the graph tell us and how do we find it (velocity time graph)
- The displacement (the distance travelled in a specific direction)
- when we see constant acceleration or deceleration, we divide the graph into shapes and calculate their total area then add them together
How to calculate the total area of a velocity time graph when the deceleration and acceleration are not constant
- Count the number of squares complete or almost complete
- estimate the number of squares remaining
- add the numbers together
- mulitiply the number of squares by the total area of one square
What is air resistance
An upward force of friction
What is it called when an object stops accelerating and moves at a constant velocity
Terminal velocity
What will a greater force of friction result in (in terms of acceleration)
A lower terminal velocity
What is it called when something is moving at a constant speed and there must be an equal force acting to the right
- The resistive forces
- they include friction with the air and friction with the road (in terms of car)
What does a resultant force cause
An objects speed to change or an objects direction
