[ملاك1]

اولا السلام عليكم ورحمة الله وبركاته
المسألة الاولى :
A balloon is filled with helium . it's volume is 1.00 m3 ......... what down word force must be applied to stop the balloon rising up into the sky ...........
( density of air = 1.29 kg/ m3 )
( density of helium = 0.18 kg/m3 ) ????

المسألة التانية :
two masses are connected by alight that passes over a frictionless pulley , as in figure , if the incline is frictionless and if m1 = 2.00 kg , m2 = 6.00 kg , and (tita) =55 degree ,,,,,,, find :
1) the acceleration of masses
2) the tension in the string
3) the speed of each mass 2 s after being released from rest ?
توجد رسمة لكن لاأعرف كيف ارسمها ... اتمنى ان تكون المسألة واضحة من غير الرسم

المسألة التالثة :
where must a weight be hung on a pole , of negligible weight ,, so that the boy at on end supports 1/3 as much as the man at the man at other end ??
يضا هنا توجد رسمة ... لكن اتمنى ان تستطيعو حلها من دونها.....

اتمنى منكم المساعدة بما أستطعتم ولكم مني خالص الشكر والتقدير
************** دمتم بود *************

[Einstein Uae]

السؤال الأول :

Buoyant force = weight of displaced air
= density of air × volume × g
= ρaVg .
Weight of balloon = density of helium × volume × g
= ρhVg .
Downward force required = ρaVg - ρhVg = (ρa - ρh)Vg
= 10.8 N.

[Einstein Uae]

السؤال الثاني :

a) The forces are gravity Fg (downward) and tension T (upward), and the object is moving

the force balance on the 2kg mass

m*a = T - mg

you will get an equation of terms of T and a

do the same but now for the 6Kg mass

now u r going to have to equations in terms of T & a

so substract them to eliminate T and find a =??

part b ) Substitute the value of the acceleration you found in part a into the equations you got above to find T= ??

part c ) speed = acceleration * time

it is easy now ^^