Physics - Forces, Levers And Moments Of Forces Flashcards
What is a force?
It’s anything that tries to change the shape, direction or velocity of a body
There are many different types of forces. Name three
Pushing, pulling, bending, squeezing, twisting, stretching
What is one of the most important forces?
The pull on gravity, which we call weight
What is force measured in?
Newtons (N)
What is weight?
Weight is the gravitational force from the earth
How are mass and weight related?
They are related by the force of gravity
What is the equation for weight?
Weight = mass x gravitational force
What is friction?
Prevents easy movement between two objects in contact
The tougher the faces of two surfaces which are in contact…
The greater the friction and the less likely they will slip
Give an example of things of high friction?
Sandpaper, car tyres, rough soled shoes
Give examples of low friction objects?
Wet surfaces, soap, ice and glass - these are all slippery
How do we reduce friction?
We lubricate, using oil or grease
Give an example where friction is useful
It is used to slow cars down when the brakes come into contact with the wheels
To investigate the relationship between the extension of a spring and the applied force [experiment]
Procedure : 1. Set up apparatus and get the natural length of the Spring
2. Attach a weight to the spring, notice new length
3. Subtract the natural length of the Spring to get the extension
4. Add a new weight. Measure extension.
5. Make a table of your results and plot a graph of extension against force
Result : graph (force, weight in newtons= 0,2,4,6,8)
(extension = 0,4,8,12,16)
Conclusion : the graph is a straight line. This shows that the extension is proportional to the force that caused it
What is a lever and give an example
A lever is any rigid body that is free to turn about a fixed point, called a fulcrum eg, a door, wheelbarrow, a seesaw and a spanner
What is the moment of the force?
It is the turning effect of the force
What two things does the moment depend on?
The size of the force (newtons) The distance (metres) from the fulcrum to where the force is applied
How would you find the moment of a force?
Force x perpendicular distance from the force to the fulcrum
What is hooke’s law?
It’s the law that states the extension of a spring is directly proportional to the force that caused the extension
To investigate the law of the lever [experiment]
Procedure :
1. Hang a metre stick from a stand
2. Adjust the metre stick until it is balanced. It is at its centre of gravity
3. Hang the two weights on the metre stick until the lever is balanced
4. Calculate the moments on the left side and on the right side by multiplying the force by the perpendicular distance in each case
Results : 20N x 0.3m = 15N x 0.4m
Conclusion : When an object is balanced, the moments on the left equal the moments on the right
