What are contact forces?
Contact forces include friction, drag, up thrust, and reaction.
What are non-contact forces?
Non-contact forces include weight, magnetic force, electrostatic forces, and gravitational forces.
How is the size of a force represented?
The size of the arrow represents the size of the force.
What is friction?
Friction is the force that opposes movement caused by contact between two surfaces.
What factors affect friction forces?
Mass of the object, shape of the object, and the surface that it is on can affect the friction forces.
What is streamlining?
Streamlining reduces friction and drag forces.
What is a resultant force?
The resultant force is a single force that has the same effect as all the forces acting on the object.
How are arrows representing forces combined?
Arrows in the same direction are added and arrows in the opposite direction are subtracted.
What does a zero resultant force indicate?
A resultant force of zero can mean the object is stationary or moving at a constant speed.
What does a non-zero resultant force indicate?
A resultant force that is not zero can mean the object is accelerating or decelerating.
What does Hooke’s Law state?
Hooke’s law states that the extension of a spring is proportional to the force applied unless the elastic limit has been reached.
What is the spring constant?
The spring constant (K) describes the stretchiness of the springs; the higher the number, the stiffer the spring.
What is the formula for force in relation to spring constant and extension?
Force = spring constant x extension.
What is work done?
Work done = distance x force.
When is work done on an elastic object?
Work is done on an elastic object when its shape changes and it stores elastic potential energy.
How is weight measured?
Weight is a force and is measured in Newtons, while mass is measured in kilograms.
How long is a day?
Day and night is 24 hours long; it is the amount of time for the Earth to rotate once fully on its axis.
How long is a year?
A year is 365.24 days long; it is the amount of time for the Earth to complete one full orbit around the sun.
Why is summer hotter?
The summer is hotter because the sun’s rays are spread over a smaller area when the Earth is tilted towards the sun.
What are luminous objects?
The sun and stars are the only luminous objects; everything else reflects light.
What are the phases of the moon?
The moon appears to change shape as the amount of the moon visible from the Earth changes.
What is a solar eclipse?
A solar eclipse is when the sun’s light is blocked by the moon.
What is a lunar eclipse?
A lunar eclipse is when the moon cannot be seen because it is in the Earth’s shadow.
What is the order of objects in the universe by size?
Objects in our universe in size order are comet, moon, planet, star, solar system, galaxy, and universe.
