rocket science (1 Viewer)

[mr EaZy]

what equations do we need to know about it?

theres a = T-mg/m
the momentum equations p=mv

anything else?


also correct me here:
when an elevator moves up

net force= ma-mg hence F=m(g+a)?? i dont why but i keep writing this down in my test papers for some reason.

what about elvators going down?

thnx

 

[gordo]

i think it is mg-f(elevator) = normal force

 

[helper]

Net force is always = ma

For going up
T-mg = ma
T=thrust or driving force up.

 

[mr EaZy]

so what is the force acting on the passengers in the elevator?

 

[helper]

Going Up

Net Force = ma

Force of Floor = ma+mg

Going Down
Net Force=ma

Force on Floor= mg-ma

 

[CrashOveride]

When going up in the elevator shudnt it exert a force of mg+ma not ma-mg?
anyone who feels they want to clarify may do so, i thought i knew this :/

 

[helper]

You right I got that wrong. Fixed them

 

[CrashOveride]

can you explain how u got the force on floor?

 

[gordo]

wen the elevator is going up, the force on the floor is the normal force of u back down on the floor

so force going up is t-mg
so normal force is t-mg + mg cause of gravity

therefore the force on the floor = the thrust of the elevator upwards

 

[breaking]

does anyone have the lyrics for rocket science - being followed?

 

[CrashOveride]

ok gordo but what abot going down ?

 

[mr EaZy]

yeah i thought net force on passengers = ma +mg but i got confused in these threads coz for some reason ive never seen the expression t-mg or anything with "T". anywza

 

[CrashOveride]

anyone wanna tell me what how to derive when its going down

 

[jumb]

um, doesnt Everything goes down?

 

[helper]

Force net = ma

Assume down positive, and accelerating down

F_g-Force Floor (T) = ma
mg-T=ma
mg-ma=T
T=mg-ma

 

[mr EaZy]

u have to recognise that ma is the net rersultant force.
now this is determined when 2 forces :gravitational (weight) force and the energy given to the lift in the form of a force are added.

so mg-T =ma since T is directed upwards??? huh! i would think of it as
mg + T = ma coz they are both directed downwards..... hmmm

ill get to u guys back on this