some MC q's (1 Viewer)

[clever angel]

hi

can someone answer these q's plzz

a cube shaped probe with sides 100m flies past a space station. an observer on the psace station measured thw width of the probe to be 85 m. wat does this observer measure the height of the probe as?
a) 85m
b) betwen 85-100m
c) 100m
d)unable to determine from data

sorry i don;t have the answer to this q'n

a rocket is just about to lauch onto a distant planet whose gravitational field strenght is greater than earth, it is decelrating uniformly as it descends. the reaction force from the seat during landing on the astronaut is

a) less than reaction force she would feel at rest on earth
b)less than reaction force she wud feel if she were at rest on planet
c) gretaer thna the reaction force she wud feel if she were at rest on earth
d) equal to her weight force on the planet

 

[serge]

Question 1) 100m

launch onto a planet?
do you mean land...

 

[Jago]

q1 is c), as the HEIGHT of a spacecraft is not affected by length contraction


and i have no idea of q2, so im going to guess a)

 

[jemsta]

q2) i think its c because since the planet has a greater acceleration due to gravity that means the planets mass would have to be grater than earth's so therefore it must have a greater reaction force

 

[serge]

it sucks that there's no answer
I remember that if you're free-falling
you're meant to feel weightless?
so im thinking it might be B

 

[mcs]

That 2nd question is a nasty one- a damn poorly worded question that is for sure. For I think if the spacecraft is decelerating on the way down then the force going against the force downwards due to the gravity would have to be pretty large- so thus without much real decent reasoning I would say C) only cause it seems to be the only one that makes sense. Cause D) wont be right cause the spaceship is deaccelarating and A and B Its not going to be less.

 

[jake2.0]

aren't (b) and (d) the same ??

 

[serge]

nope,
one's equal to the other is less than

 

[helper]

The second one is really poorly worded.
The answer is C, because to slow the person down, the reaction force has to be greater than the gravitational force. The gravitational force is greater than the gravitational force on Earth.
As the reaction force is equal to the gravitational force, if you are at rest, the reaction force slowing you down has to be greater than the rest reaction force.

Q1, the answer is C but is one I don't like and have argued about before, as you are not told which direction the craft flies past at. The height won't change as long as it flies past, perpendicular to the height, which you aren't told. So I still argue D is the better answer.