Physics Unit 3 Quiz 1

contact forces

contact between objects

field forces

involve no physical contact between objects

examples of field forces

gravity (downward acceleration), magnetic fields, and electricity (static)

weight is the

acceleration of gravity acting on our mass opposed by the floor preventing you from falling

Drawing Free Body Diagrams

1. draw force due to gravity (or force by the earth

2. Draw for due to the ground (force upwards by ground)

3. Draw sideways forces

Newton’s First Law

Objects in motion stay in motion and objects are rest stay at rest unless acted on my a net external force

If an object has no acceleration, does it have net force

no

When a vehicle is at a constant speed, does it have a net force

NO

no acceleration=no net force

when a force is applied to an object with mass it…

accelerated

inertia

an objects tendency to keep moving if its already moving

If two objects are being pushed with the same force which one will have a greater acceleration

the object with the smaller mass

iniertia is proportional to

the objects mass

if the force arrows cancel out, what it the net force and why

0 because no acceleration

A car with a velocity of zero only has what two forces acting on it

Fgravity and Fground

A car with a constant velocity has what forces acting on it

The force of gravity

force of ground

force of engine moving in right direction

force of resistance moving left

in a constant velocity what must happen to all force arrows

they must all cancel out

if you have a net force, what should you do to calculate it

1. redraw

2. find the angle between force of gravity and force of ground

3. find x and y components (using sin and cos)

4. add up x and y directions

5. 
   

equilibrium

forward reaction rate=backwards reaction rate

dynamic equilibrium

the pull of something downwards and upwards with the same acceleration

In which parts of a velocity v time graph is the graph expierencing a net force

parts where the graph does not have a constant/zero velocity (slope greater than 0

if you are given 4 forces that are acting on an object ans asked to find the magnitude and direction what must you do?

1. find difference between the two directions

2. find which one is greater and use that angle

3. pythagorean theorem

4. add directions together to get final direction

Newton’s second law

more force creates more acceleration on an object and a force on a heavy object with a lot of mass will cause less acceleration than when applied to a ligher object

F=ma

How do you know which direction the acceleration will be in when given net force and mass

It is going to be the same direction as the NET FORCE

F=ma

Newton’s Third Law

if you have two objects toucbing you are going to have two equal but opposite forces

Each object only expierences

its own force

the hypotenuse of a triange is equal to

a line that splits the triange in half (diagonal line direction)

to have force pairs what much you have

CONTACT!

what force is a scale recording

the upward force on the persons feet (F_N)

Force=

Mass x Acceleration

gravity on another planet is still going to be

NEGATIVE

F_N is always going to be

POSITIVE EVEN WITH NEGATIVE GRAVITY

apparent weight

weight that the person feels

how to find apparent weight

add weight using acceleration given and true weight together

fundamental units for force (N)

kgm/s²

can an object be at equilibrium if only one force acts on it? Why?

no because the vector forces must cancel out and one force must have an equal but opposite force for there to be equillibrium.

if a questions asks you to find the magnitude to the net force what shpuld you do

mass x acceleration

why will a person feel lighter and have a lighter weight if they are on an elevator acceleration downwards?

because the force of the elevator floor pushing up on you is less. The downward acceleration of the elevator reduces the force that the elevator is exerting making you feel lighter

if you are asked to find the weight of a person if they were on an elevator what should you do

1. find weight of the person on earth (not elevator)

2. find net force acting on the person in the elevator (either downwards or upwards)

3. add/subtract the values depending on whether its upwards or downwards.