Ns-Term 3 - Unit 1: Forces pg 205-224 Flashcards
what is a force?
it is a push or pull
what unit is force measured in?
It is measured in newton (N)
name 5 possible things that could happen if force is exerted on an object
- speeding up or slowing down
- deformation
- rotation
- direction can change
- object can come to a standstill
how to forces always act?
forces always act in pairs
Define force pairs
forces of equal magnitude which simultaneously work in opposite directions
what are the two types of forces and explain what happens in them.
- non-contact or field forces
• work over a distance (action-over-a-distance) - contact forces
• object touches another object
give examples of non-contact/ field forces
- gravitational forces
- magnetic forces
- electrostatic forces
give examples of contact forces
- mechanical forces
- applied force
- friction forces
- normal force
- tension force/tension
- air resistance
- elastic forces in springs
What is gravitational force?
force with which the earth attracts objects
give examples of of objects that attract each other
- the sun and planets
- earth and moon
- earth and objects on earths surface
what direction is gravitational attractive force?
it is always towards the center of the object
define mass
an indication of the amount of matter and is measured in kilograms
(the mass remains constant)
define weight
attraction force that the earth (or a planet) exert on an object. It is measured in newton
(weight changes)
do the masses and radii of planets differ?
yes, the masses and radii of planets differ; therefore the attractive force exert by each planet on objects differ
write down the formula to calculate weight
Fg=w=mg
e.g.
An astronauts mass is 100kg. calculate his weight on earth and on the moon
Earth: Moon:
Fg=w=mg Fg=w=mg
= (100)(9,8). = (100)(1,6)
=980N =160N
define magnetic forces
force with which magnetic substances attract or repel each other
name the 3 metals that magnets attract
iron, nickel, cobalt
what are materials that are attracted by magnets known as?
ferromagnetic substances
what are the two types of electrical charge?
- positive charge
* negative charge
what happens in a positive charge?
the object releases electrons
what happens in a negative charge?
objects accept electrons
what does an atom consist of?
•protons (+charge)
•neutrons (neutral charge)
(both in the nucleus)
•electrons (- charge)
(space around the nucleus)
how is energy stored in cells?
It is stored in the form of potential energy
explain how lighting is formed
- particles and droplets in clouds rub and bump against each other, and become charged
- big amounts of negative and positive charges are separated
- lot of the negative charges accumulate mainly in the bottom part of the cloud and positive charges in the top part
- these separated charges causes potential energy
- when discharged, it is converted into electrical energy and then converted into light and heat energy
