Forces (2) Flashcards
What is a force
contact forces-
non-contact forces-
a force is a push or a pull
contact forces- two object have to touch for a force to act (friction)
non-contact forces- two objects don’t need to touch for a force to act (gravity)
Scalar quantities-
Vector quantities-
Scalar quantities- a quantity with only magnitude (speed)
Vector quantities (forces)- a quantity with direction and magnitude (velocity)
what is weight
weight is the force acting on an object due to differing gravitation field strengths (earth’s is 9.8)
weight = mass x gravity
Resultant force
the total force acting in one direction
if a resultant force moves an object, work is done
Resultant force diagrams
- draw the forces acting on an object as lines
- join the two together with a diagonal line
- measure the magnitude (distance) of the line and the direction by measuring the angle using a protractor
What is elasticity
What is elastic deformation
the property of an object that can be stretched, compressed or bent and then return to its original shape
elastic deformation is when the object doesn’t return to its original shape
Investigating springs practical
- Set up the clamp stand and attach the spring securely.
- Hang a ruler vertically next to the spring, ensuring the zero mark is level with the bottom of the spring.
- Measure and record the original length of the spring (unstretched).
- Add a known mass to the spring and allow it to settle.
- Measure and record the new length of the spring and calculate the extension
- Repeat, adding more masses one at a time, and record the results.
what is a moment
how is it increased
where is the maximum moment achieved
the turning effect on a pivot of a force
a larger force or lever increases the moment
the maximum moment is achieved at right angles to the pivot
What are levers
levers make it easier to do work, as the distance from the pivot is increased so less force is needed to achieve the same moment
What are gears
how can they change the moment of a force
gears transmit rotational effects
different sized gears can be used to change the moment of a force
(a bigger gear causes a bigger moment and turns more slowly than the smaller gear)
Fluid pressure
what does pressure depend on
Fluid pressure is because of particle collisions exerting a force on the container
It acts equally in all directions in a fluid at rest.
It increases with depth in liquids, as there are more particles above the point
Pressure depends on density of the substance
Upthrust
sink/float
Upthrust is the upward force exerted by a fluid on a submerged object.
It occurs because pressure in a liquid increases with depth, meaning the pressure on the bottom of an object is greater than the pressure on the top.
This pressure difference creates a net upwards force, known as upthrust.
If the upthrust is greater than or equal to the object’s weight, the object floats; otherwise, it sinks.
the upthrust on an object is equal to the weight of the fluid it displaces.
Objects with an average density lower than the fluid will float, while those with higher density will sink.
Atmospheric pressure
Atmospheric pressure is the pressure exerted by air molecules in Earth’s atmosphere due to their weight.
It acts in all directions and decreases as altitude increases because there are fewer air molecules at higher elevations.
As altitude increases the number of air molecules above decreases
Therefore, atmospheric pressure decreases.
walking speed-
running speed-
cycling speed-
walking speed- 1.5m/s
running speed- 3m/s
cycling speed- 6m/s
Distance-time graphs:
gradient:
Steep gradient:
Gentle gradient:
Horizontal line:
A straight line with a positive gradient:
Curved line:
Upward curve:
Downward curve:
Horizontal line:
A graph that shows how distance changes over time.
Distance is always a positive value, as it measures how far an object has moved, regardless of direction.
Gradient: The gradient represents the speed
Steep gradient: High speed (fast movement).
Gentle gradient: Low speed (slow movement).
Horizontal line: No movement (distance does not change).
A straight line with a positive gradient: The object is moving at a constant speed.
Curved line: The object is accelerating or decelerating
Upward curve: Acceleration
Downward curve: Deceleration
Horizontal line: The object has stopped
Velocity-time graphs:
Gradient:
Positive gradient:
Negative gradient:
Curve:
Horizontal line:
Area under the graph:
Above the x-axis:
Below the x-axis:
Flat section:
A graph that shows how velocity changes over time.
Velocity can be positive or negative, indicating direction (e.g., forwards or backwards).
Gradient: The gradient represents acceleration
Positive gradient: Positive acceleration
Negative gradient: Negative acceleration
Curve: changing acceleration
Horizontal line: Constant velocity (no acceleration).
Area under the graph: Represents displacement (distance in a specific direction).
Above the x-axis: Positive displacement (moving forwards).
Below the x-axis: Negative displacement (moving backwards).
Flat section: No change in velocity (constant velocity).
What is the correlation between resistance (friction) and speed
resistance increases as speed increases
What is terminal velocity
the maximum speed an object will reach when falling before falling at a constant speed
Newtons first law
An object will remain at rest or continue moving with a constant velocity unless acted upon by an external force.
Newtons second law
The force acting on an object is directly proportional to its mass and the acceleration it experiences F=AM
acceleration is inversely proportional to the mass of the object
Newtons third law
When two objects interact, the forces they exert on each other are equal and opposite
What is inertia and inertial mass
Inertia is the tendency of an object to stay at rest
It is the property of matter that keeps objects at rest or in motion at a constant speed unless acted upon by an external force
An objects inertial mass measures how difficult it is to change the velocity of an object
This can be found using F=AM
Investigating motion (second law) practical
F=
A=
M=
Attach a trolley of known mass with a piece of card to a pulley with masses on the end
Use two light gates to measure how long it takes the object to travel a set distance.
Calculate acceleration by dividing the set distance by the time between the two light gates
Newton’s second law links to the results:
F= weight of the hanging masses
A= the acceleration of the trolley
M= mass of the whole system
What is stopping distance comprised of
stopping distance = thinking distance + braking distance
