some questions (1 Viewer)

[clever angel]

a person stood on the scales that were designed for earth whislt on amrs. the scale gace a reading of 50 kg. what is the actual mass of the prson
a. 132.4 kg
b. 50 kg
c. 18.9 kg
d. 490N
(Use g= 9.8 for earth and 3.7 for mars)
according to my teacher the ans is a

question 2
80% of the initial mass of the rocket is propellant. after 80 sec during the lauch the ist stage hass used up all its fuel and disengages from 2nd stage. ten seconds later the 2nd stage ignites and burns for 60 sec

sketch a graph to show how velocity varies with time?
if the rocket hass a mass of 2.8*10^6 kg and the 1st engiens have a thrust of 36*10^6N calculate
the intitial acceleartion'
the g force on the astronaut during lift off

 

[香港!]

a person stood on the scales that were designed for earth whislt on amrs. the scale gace a reading of 50 kg. what is the actual mass of the prson
a. 132.4 kg
b. 50 kg
c. 18.9 kg
d. 490N
(Use g= 9.8 for earth and 3.7 for mars)
according to my teacher the ans is a

The scale is designed FOR Earth... so it will take the weight force on that scale and divide by 9.8 to show the mass.
W\9.8=50
W=490
So the mass of the person is actually 490\3.7=132.4 since the person is on mars..

 

[serge]

for the first question u could jus discard a,b and c since it asks for weight not mass so d has to be the only option because its in Newtons, not kg

what is the actual mass of the prson

they ask for mass, not weight, so it must be kg

 

[suchet_i]

Originally Posted by clever angel
a person stood on the scales that were designed for earth whislt on amrs. the scale gace a reading of 50 kg. what is the actual mass of the prson
a. 132.4 kg
b. 50 kg
c. 18.9 kg
d. 490N
(Use g= 9.8 for earth and 3.7 for mars)
according to my teacher the ans is a

ok bfore i say the answers.. i wanna say that scales r screwed up.. well they are actually measuring weight instead of mass so they should b in newtons.. u can get confused!
w = mg
w = 50*9.8
= 490
weight on mars is 3.7/9.8 times wat it is on earth ==> 185 N
and then we use w= mg
185 = m * 3.7
m = 50
:S hmm may b its 50 lol?
c thats the thing.. scales should be in newtons!!!
dam now this has got me confused some 1 answer this question properly

 

[helper]

ok bfore i say the answers.. i wanna say that scales r screwed up.. well they are actually measuring weight instead of mass so they should b in newtons.. u can get confused!
w = mg
w = 50*9.8
= 490

You went wrong here. The scales measure weight as you said, so the force they measure on Earth, is the same as the Force they measure on Mars, they are just calibrated to measure kg, as you showed above.

So the weight being exerted on Mars is still 490N. The acceleration due to gravity, does not change what the force being exerted on the scale is.

Think of the cheap spring balance scales you can use, probably did at school. On one side is kg and the other is Newtons. The Newtons side will still read the same if calibrated for Mars, they would just redo the kg side.

weight on mars is 3.7/9.8 times wat it is on earth ==> 185 N
and then we use w= mg
185 = m * 3.7
m = 50
:S hmm may b its 50 lol?
c thats the thing.. scales should be in newtons!!!
dam now this has got me confused some 1 answer this question properly