Physics Question help!! (1 Viewer)

[wiliaamnguuyen]

So a shuttle is decelerating at a rate of 50m/s. Travelling towards the Earth. A dude is 90kg in the shuttle, what is the force of the seat on the dude? Taking into consideration of the deceleration and gravitational force of the guy.

Questions very confusing, if anyone wants the answer, just ask me!

 

[Drsoccerball]

Is the answer 932 N ?

 

[wiliaamnguuyen]

Yeah it is! Can you show me how you worked it out?

 

[wiliaamnguuyen]

Actually the answer is 5382N

 

[Drsoccerball]

Yeah it is! Can you show me how you worked it out?

Okay so i kind of used extension 2 knowledge of mechanics to solve (which is just memorised in HSC physics)
the formula = 932N OR as you memorise F=T-mg and since T is negative you get the formula F=T+mg (Assuming downwards is positive direction)

 

[Drsoccerball]

my bad you have to multiply acceleration by the mass aswell
F= 90x9.8 +50x9.8 =5382

 

[wiliaamnguuyen]

Wait, why do you add them? The decelerating force is pushing against the shuttle causing it to decelerate. So shouldn't it be 4500-982N?

 

[Drsoccerball]

Wait, why do you add them? The decelerating force is pushing against the shuttle causing it to decelerate. So shouldn't it be 4500-982N?

Because its the rate decreasing

 

[wiliaamnguuyen]

Could you provide a stronger explanation why you add them? I just don't understand why lmao

 

[Drsoccerball]

Could you provide a stronger explanation why you add them? I just don't understand why lmao

IF its traveling towards earth that means acceleration is towards the earth but that acceleration is slowly decreasing as t increases

 

[wiliaamnguuyen]

Ohhhh!!! Thank you!! I get it now

 

[Drsoccerball]

If both positive (assuming g=10 for ease):








Since u<0 therefore answers wrong
You minus my bad

 

[wiliaamnguuyen]

Dammit! My friend was right then. Thanks Drsoccerball!!

 

[Fizzy_Cyst]

You should be adding them, not subtracting.

If it is moving towards Earth, but decelerating, then the acceleration is opposing the motion of the craft (and opposing acceleration due to gravity!). So, the 'relative acceleration' is 50 + 9.8 = 59.8, therefore weight = 59.8 x 90 = 5382N.

It is analogous to an elevator travelling downwards, but slowing down. You feel heavier than you really are!

Think of it this way, if you subtract it, then using your friends method, if acceleration was 9.8 upwards, then you would appear weightless!!

 

[Drsoccerball]

You should be adding them, not subtracting.

If it is moving towards Earth, but decelerating, then the acceleration is opposing the motion of the craft (and opposing acceleration due to gravity!). So, the 'relative acceleration' is 50 + 9.8 = 59.8, therefore weight = 59.8 x 90 = 5382N.

It is analogous to an elevator travelling downwards, but slowing down. You feel heavier than you really are!

Think of it this way, if you subtract it, then using your friends method, if acceleration was 9.8 upwards, then you would appear weightless!!

I did the calculations and you get t as negative if its both positive therefore it had to be negative

 

[Mr_Kap]

I'm confused now. Is it negative then or not?

 

[Fizzy_Cyst]

I did the calculations and you get t as negative if its both positive therefore it had to be negative

I think you ar misreading or misinterpreting the question.

Moving towards the Earth but decelerating at 50m/s^2 is the same thing as moving away from the Earth and accelerating at 50m/s^2.