MindMap Gallery Force and Machinery - Junior High School Physics
Force and machinery - junior high school physics, force and machinery are two important concepts in physics. Force is the interaction between objects, which can deform an object or change its state of motion.
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The ice hockey schedule for the Milano Cortina 2026 Winter Olympics, featuring preliminary rounds, quarterfinals, and medal matches for both men's and women's tournaments from February 5–22. All game times are listed in Eastern Standard Time (EST).
This Valentine's Day brand marketing handbook provides businesses with five practical models, covering everything from creating offline experiences to driving online engagement. Whether you're a shopping mall, restaurant, or online brand, you'll find a suitable strategy: each model includes clear objectives and industry-specific guidelines, helping brands transform traffic into real sales and lasting emotional connections during this romantic season.
This Valentine's Day map illustrates love through 30 romantic possibilities, from the vintage charm of "handwritten love letters" to the urban landscape of "rooftop sunsets," from the tactile experience of a "pottery workshop" to the leisurely moments of "wine tasting at a vineyard"—offering a unique sense of occasion for every couple. Whether it's cozy, experiential, or luxurious, love always finds the most fitting expression. May you all find the perfect atmosphere for your love story.
The ice hockey schedule for the Milano Cortina 2026 Winter Olympics, featuring preliminary rounds, quarterfinals, and medal matches for both men's and women's tournaments from February 5–22. All game times are listed in Eastern Standard Time (EST).
Force and Machinery
Force (expressed as F)
Definition: The effect of an object on an object
The object that exerts force is called the force-exerting object, and the object that receives the force is called the force-receiving object (the action of force is mutual)
Force cannot exist without objects. The generation of force must involve two objects (objects in contact with each other do not necessarily produce force)
The unit of force in the International System of Units is expressed in Newtons (indicated by the letter N)
Three elements
Size
direction
point of action
force diagram
Three elements
Size
direction
point of action
The schematic diagram reflects the three elements
The length of the line segment represents the size
The arrow points to the direction
The starting point of the line segment represents the point of action
Things to note
After you finish drawing, mark the name and size of the force.
If multiple forces appear in the schematic diagram, pay attention to the magnitude of the forces
gravity
Definition: The force exerted on an object by the attraction of the earth is called gravity
Use G to represent G=mg (the ratio of gravity to mass)
The gravity of an object is proportional to its mass
Take g=9.8N/kg (take g=10N/kg for rough calculation)
Direction: vertically downward (perpendicular to the horizontal plane)
center of gravity
The center of gravity of an object with uniform mass distribution is its geometric center
Increase stability
Increase the supporting area at the bottom of the object
lower center of gravity
Friction (expressed by f)
Generating conditions
Two objects are in contact with each other
Two objects move relative to each other or have a tendency to move relative to each other
The contact surface should be rough enough
Type
Sliding friction
Definition: The force that hinders the relative motion of one object when it slides on another
Direction: opposite to the direction of relative motion (trend) of the object
Static friction
Definition: When an object has a tendency to move, it will experience a force that prevents it from becoming in motion. This force is called static friction
rolling friction
Definition: The frictional force produced when one object rolls on another
Conditions that influence size
The greater the pressure, the greater the friction
Contact surfaces. The rougher it is, the greater the friction
Methods to influence size
beneficial friction
Increase the pressure at the contact surface between objects
Increase the roughness of the contact surface between objects
harmful friction
Reduce stress on the contact surfaces between objects
Reduce the roughness of the contact surfaces between objects
Turn sliding into scrolling
experiment
Using a spring dynamometer
Require
Zero calibration
Clarify the measuring range and graduation value
on the same straight line
slope car
Control variable method: same car, same height, same slope Conversion method: compare the distance the car slides
Conclusion: The smoother the surface, the smaller the resistance. The longer the movement distance, the slower the speed decreases
Things to note
The inclination of the slope should match the length of the board
Let the car slide freely from the appropriate position on the slope
The experiment should be carried out in the proper order
Control Variable conversion method ideal experiment method experimental reasoning
pulley
moving pulley
Not saving effort, changing the direction of force
F=G
fixed pulley
Save effort and do not change the direction of force
F=G/n (number of rope strands)
lever
definition
A hard rod that can rotate a fixed point
leverage balance
The lever is at rest under the action of power and resistance
elements
Power F1
Power arm L1
Fulcrum O
Resistance arm L2
Resistance F2
Leverage balance condition
F1L1=F2L2
type
Labor-saving lever
Effortful lever
equal-arm lever
draw arm
Find the line of force action
Passing the fulcrum
Make a vertical line