PHYSICS
COLLEGE

Answer: The bouyant force of water is equal to the weight of the piece of wood

COLLEGE

Light of wavelength 441.1 nm falls on two slits spaced 0.29 mm apart. What is the required distance from the slits to the screen if the spacing between the first and second dark fringes is to be 4.0 mm?

Answer: R = 0.131 m

Explanation: The formulae for the distance between a fringe and the first (center) is given by

y = R×mλ/d

Where y = distance between first and nth fringe = 4mm = 4×10^-3m

λ = wavelength of light = 441.1nm = 441.1×10^-9m

R = distance between slits and screen =?

d = distance between slits = 0.29mm = 2.9×10^-4m

4×10^-3 = R ×2 ×441.4×10^-9/ 2.9×10^-5

Hence R = (4×10^-3) ×(2.9×10^-5)/2×441.4×10^-9

R = 1.16 × 10^-7/8.828×10^-7

R = 1.16/8.828

R = 0.131 m

COLLEGE

Suppose Eratosthenes had found that, in Alexandria, at noon on the first day of summer, the line to the Sun makes an angle 30° with the vertical. What, then, would he have found for Earth’s circumference?

Answer:

6000 miles

Explanation:

The angle of the sun shone at an angle of 30° to the zenith

This means that the angle of the sector of the circle is 30° (θ)

S = Length of the sector of the circle = 500 miles (Distance between Alexandria and Syene)

r = radius of earth

Converting 30° to radians

Circumference

∴ Earth’s circumference would have been 6000 miles

MIDDLE SCHOOL

A bird flies from the South Pole to the North Pole. Part of the journey is 1000 miles that takes 2 weeks. What is the bird’s velocity in that time? Show work for credit and include final units.

Velocity = Distance / TimeHere, Distance = 1000 milesTime = 2 weeks = 14*24 Hours [ 1 week = 7 days & 1 day = 24 hours ] Time = 336 Hours

Now, substitute the values,Velocity = 1000/336 = 2.976 miles/hour

So, your final answer is 2.976 miles/hour

Now, substitute the values,Velocity = 1000/336 = 2.976 miles/hour

So, your final answer is 2.976 miles/hour

HIGH SCHOOL

Which of the following occurs in January when the earth is closest to the sun?

Which of the following occurs in January when the earth is closest to the sun?

Answer: A perihelion

Explanation: I just took the test :)