need help with physics. please variou math questions?

Question

1. calculate the speed in m/s at which earth revolves about the sun. assume a circular orbit.

2.a dike in holland springs a leak through a hole of 1 cm^2 at a depth of 2 m below the water surface. how much force must the boy apply to the hole with his thumb to stop the leak. could he do it.

Answer 1

The diameter of the earth's orbit is about 300 million km.
--> http://hypertextbook.com/facts/2004/CherisseBarnes.shtml
The circumference of the orbit is about 3.14 * 300 million = 942000000 km
= 942000000000 m

It takes roughly 365 days for the Earth to go around the Sun once.

(365 days) * (24 (hours / day)) * (60 (second / hour)) = 525 600 seconds

(942 000 000 000 meters) / (525 600 seconds) = 179223744 m / s

or about 1.8 * 10^8 m/sec



This means that the Earth is rushing through space around the Sun at a rate of about 67,000 miles per hour! The time it takes for the Earth to go around the Sun one full time is what we call a year.

Answer 2

1. Speed = distance / time
= circumference of orbit / 1 year
= 2 * pi * radiusof orbit / (365 * 24 * 60 * 60)
= 2 * 3.14 * 150 000 000 000 / (365 * 86400)

= 29870 m/s

2. Pressure = height * density * acceleration of freefall
= 2 * 1000 * 9.81
Force = pressure * area
= (2 * 1000 * 9.81) Pa * 0.0001 m^2
= 1.962 N

This force is easily provided by the boy since it is approximately equal to the force needed to lift an apple.

Answer 3

1. You need to know the radius of the Earth's orbit around the sun ~ approx. 149.6 million kilometres.

Calculate the orbit circumference using 2*PI*radius
Put that into metres (multiply by 1000)
Divide the answer by 365.25 (to get days)
Then divide by 24 (to get hours)
Then divide by 3600 (to get seconds)

You should end up close to 29,785 m/s.

Answer 4

take
mass sun=M
mass earth=m
Distance=r
G=gravitational constant
speed=v

the gravitational force between the objects=G.M.m/(r^2)
to stay in orbit gravitational pull=centrepetal force
G.M.m/(r^2)=m.v^2/r
G.M/r=v^2

2.
density of water 1000kg/m^3
pressure @ 2m:
1000*10*2=20000N/m^2

force to apply?=pressure*area
=20000*.0001
=2N

Answer 5

i am really bad at physics!!!sorry