13. A girl of weight 400 N holding a bag of weight 40 N
on her head. If she is standing on semicircular heels
of periphery 72/7cm,
, then net pressure exerted on
the floor by the girl is
Answers
weight of girl = 400 N
weight of bag held by girl = 40 N
so, net weight applied on heel = 400N + 40N = 440 N
periphery of semicircular heels = 72/7
⇒ perimeter of semicircle = 72/7
⇒πr + 2r = 72/7
⇒r(22/7 + 2) = 72/7
⇒r(36)/7 = 72/7
⇒r = 2cm
so, area of semicircular heel , A = πr²
= 22/7 (2 × 10^-2)² m²
= 88/7 × 10^-4 m²
now, pressure = Net force/area
= 440/(88/7 × 10^-4)
= 70/2 × 10⁴ N/m²
= 3.5 × 10^5 N/m²
hence, option (3) is correct choice.
Answer:
Option (3) is the right answer
Explanation:
weight of the girl = 400 N
weight of the bag = 40 N
Total weight applied by the girl= 400N + 40N = 440 N
perimeter of semicircle = 72/7
Perimeter=Circumference+Diameter
In this case Circumference will be half because circle is semi so
For complete circle Circumference=π*d=π*2*r=2πr
For semi circle Circumference=2πr/2=πr
and Diameter will remains 2*r
so,
πr + 2*r = 72/7
r(22/7 + 2) = 72/7
r(36)/7 = 72/7=72/36=2 cm
r = 2 cm
so, area of semicircle = A = πr²
= 3.1416 *(2 × 10^-2)² m²
= 12.56* 10^-4 m²
we know that
pressure = force/area= 440/(12.56× 10^-4)
= 3.5 × 10^5 N/m²
Option (3) is correct answer