Topic 5 - Forces Flashcards
What is a force?
a push or pull that acts on an object due to the interaction with another object
What unit is force measured in ?
Newtons (N)
Are forces classed as a vector or scalar quantities and why?
-vector
- because they have both magnitude and direction
what is a contact force?
the objects are physically touching
what is a non- contact force?
the objects are physically separated.
Name 4 types of contact forces
-friction,
-air resistance,
-tension
-normal contact force
Name 3 non contact forces
gravitational force,
electrostatic force
magnetic force
Is air resistance a contact or non-contact force? Explain why.
Air resistance is a contact force. This is because it is due to the physical contact (collisions) between an object and the particles in the air.
what are scalars?
quantities with a magnitude (size) only.
what are vectors?
describes a movement from one point to another. A vector quantity has both direction. and magnitude. (size).
name 4 examples of scalar quantities
-time
-temperature
-speed
-distance
Name 4 examples of vector quantities
-velocity
-displacement
- acceleration
-momentum
-force
What is meant by the term equilibrium?
when the forces acting on an object are all balanced, so the resultant force is 0
What is an elastic object?
one that regains its shape when the forces demorming it are removed
Fill in the gaps:
When an elastic object is ______________ the energy which caused it to deform is stored as ______ __________ which is released when the force is _________
-deformed
- elastic energy
- removed
What is hookes law?
the extension of a spring is directly proportional to the force applied, provided its limit of proportionality is not exceeded
F=Ke
What is the method for the hookes law practical (6 steps)?
- hang the spring to the clamp and add a splint so its easier to read the length
- check that the splint is horizontal. take a reading on the ruler(lenght of unstretched spring at weight 0.0N)
- hook the 100g mass hanger on the bottom of the spring. (1N)
- take a reading of the length of the spring
- add further masses(100g each time) and measure and record the length of the spring for at least 8 times
- calculate the extension.by subtracting unstretched spring lenght from each length recording
What is an objects spring constant?
a measure of how many Newtons of force it would require to stretch (or compress) the object by 1 metre. It has the units
N/m.
Fill in the blank:
Objects with a _____________ spring constant are more stiff, so they require_____force to stretch.
Objects with a higher spring constant are more stiff, so they requiremoreforce to stretch.
what does each symbol represent in this equation (hookes law)?
𝐹=𝑘e
Fis the force applied to the spring,𝑘is the spring constant, and𝑒is the extension.
If you stretch an object too much it can pass its ‘elastic limit’ (also known as the ‘limit of proportionality’).
At this point what will happen to the object?
It will start deforming inelastically
Fill in the blank:
objects with a __________ spring constant are more elastic so they require _____ force to stretch
lower
less
What is the equation to work out the elastic potential energy of an object?
𝐸𝑒=1/2𝑘𝑒²
what do the symbols in this equation represent?
𝐸𝑒=1/2𝑘𝑒²
𝐸𝑒 (elastic potential energy J)
𝑘 (spring constant N/m)
𝑒² (extention m)
In a graph representing hookes law, The gradient of the straight part of the graph tells us the:
spring constant
In a graph representing hookes law, The area under the curve tells us the:
Elastic potential energy
In a graph representing hookes law, The point where the line goes from straight to curved is referred to as the:
Limit of proportionality
or
Elastic limit
What is a moment?
the turning effect of a force around a fixed pivot
What is the formula for moment?
Moment (NM)= force(F) x Distance from pivot (m)
What would happen to an object if the forces are balanced and the resultant force is 0?
the object will stay in the same state of motion
What is the resultant force of an object?
the single overall force acting on an object
What two things does the size of a moment depend on?
-size of force
- perpendicular distance between force and pivot
What is the equation that links weight mass and gravity?
Weight (w) = Mass (m) x gravity (g)
What is the equation that links pressure force and area?
Pressure (Pa) = force (N) / area (m²)
How can you increase the pressure on a given point in a fluid?
increase the height of the fluid above the point
The pressure in a liquid depends on: (2 things)
-density of liquid
- depth
What is the unit for pressure?
pascals (Pa)
What is the formula for pressure in a liquid?
Pressure (n/m²) = density x gravity x height
True or false:
air pressure is equal in all directions
true
What is air pressure caused by?
the force of air gas particles bumping into things
What is upthrust?
the upward force that a fluid exerts on a body floating in it
An object floats when its weight is _______ to the _____________ provided by the liquid
equal
upthrust
An object sinks when its weight is __________ than the __________ provided by the fluid
greater
upthrust
Pressure in a gas is caused by particles ____________. the more frequent collisions and the greater their force, the ___________ the pressure
colliding
greater
IS distance a scalar or vector quantity and why?
-scalar
- it only has a magnitude and is a measure of how far an object has travelled
IS displacement a scalar or vector quantity and why?
- vector
- has magnitude and direction
What is the equation that links speed distance and time?
speed (m/s) = distance/ time
What is the equation that links velocity displacement and time?
velocity (m/s) = displacement/ time
what is acceleration?
the rate of change in velocity
What is acceleration measured in ?
m/s²
What is the equation for acceleration if given the time?
acceleration = change in velocity / time taken
What is the equation for acceleration if distance is given?
acceleration = final velocity² - initial velocity²
As the velocity of a falling object increases, the air resistance:
increases
Terminal velocity is reached when:
The resultant force is zero
and
The weight has the same magnitude as the air resistance
What does newtons 1st law state?
if forces acting on an object are balanced then if it is still it will stay still and if it is moving it will keep moving at a constant speed in a straight line
what does newtons 2nd law state?
A resultant force will cause an object to accelerate in the direction of the force. the acceleration is directly proportional to the force and inversley proportional to the mass Force = mass x acceleration
What does newtons 3rd law state?
for every action there is an equal and opposite reaction however the force mut be of the same type
What is momentum?
the tendency of an object to keep moving in the same direction
Is momentum scalar or vector?
vector
What is the equation that links momentum (kg m/s) mass and velocity?
momentum= mass x velocity
What does the conservation of momentum state?
in a ‘closed system’ the total momentum before an event is equal to the total momentum after the event
