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# Tag Archives: Materials and Supplies

## The curvature of earth and a metal pipe!

I’ve been wondering about the following issue for the past few days, let’s assume all terrain on earth is plain, we have infinite supply of straight pipe sections we can assemble into a very straight long pipe all over the equator, if we observe a small part of the pipe let’s say, 10 or 100 meters it would appear straight, but as a whole, would it continue to be so straight that it would form an increasing angle with the surface as the planet’s surface becomes curved? Or would the pipe become ring along the planet? and in this case, how could it become a ring if it’s all straight pieces of rigid metal pipe? because of the curvature of space due to gravity? or because long things tend to bend in proportion to how narrow or thick they are respect to the lenght?? English is not my mothertongue, I hope i made myself clear enought in depicting the esense of my question. Thank you.

Posted by Jesus Bitar

## Refraction – Disappearing letters

A rectangular block of glass is placed on a printed page lying on a horizontal table. what is the minimum value of u of glass so that the letters on page are not visible from any of the vertical faces of the block.

Asked Kushagr

## Numerical (MCQ) from Kinematics

A person standing on an escalator takes time t1 to reach the top of a tower when the escalator is moving.he takes time t2 to reach the top of the tower when the escalator is standing.how long will he take if he walks up a moving escalator?

a)t2-t1 b)t1+t2 c)t1t2/(t1-t2) d)t1t2/(t1+t2)

**OPEN TO VISITORS TO MAKE A TRY**

*Please post your answers as comments*

## Numerical Problems from Kinematics

1. A stone is thrown in a vertically upward direction with a velocity of 5 m s-1. If the acceleration of the stone during its motion is 10 m s–2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

2. Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?

3. A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

4. A ball thrown up vertically returns to the thrower after 6 s.

Find

(a) The velocity with which it was thrown up,

(b) The maximum height it reaches, and

(c) Its position after 4 s.

###### Related articles

- Kinematics – Signs of displacement and Velocity (askphysics.com)
- Numericals on Freely falling bodies (askphysics.com)

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