Mechanics | Relativity Answers

A wooden cube is floating in water with 2cm of it above the water level. As 100g mass is placed on its
surface, the cube goes down by 1cm. Determine the mass of the cube.

A car was moving with a velocity 24ms-1
. Suddenly the driver saw a child on his way, just 8m away from
the car. The driver immediately pressed the brakes. But it was too late; the car skidded to a halt at 12m.
What was the velocity of the car at the moment when it ran over the child?

It takes 3s for a sound wave to travel to a point 1km above the water surface from its source which is
kept under the water at a depth of hm. Determine the value of h, if it is given that velocity of sound in air
is 340ms-1
and in water is 1420ms-1

Two hills have 700m distance between them. A man fired with a gun standing between these two
hills. He heard the 1st echo after 1s of firing and 2nd echo after 3s of firing. Determine the
temperature of that place in Celsius scale. Velocity of sound in air at 0
0C is 332m/s.

If a sound is made in one end of an open iron tube of 1050m two sounds are heard at the other
end with an interval of 2.8 sec. If the velocity of sound is 350m/s in air, what is it in the iron?

A stone is dropped into a well. The splash is heard 2.95 seconds later. What is the
depth of the well? Velocity of sound in air is 350 m/s.

Suppose that, while lying on the beach near the equator watching the sun set over a
calm ocean, you start a stop watch just as the top of the sun disappears. You then
stand, elevating your eyes by a height H=1.70m, and stop the watch when the top of
the sun again disappears. If the elapsed time is t=574s, what is the radius of the
earth?

A rough slope of length 5m is inclined at an angel of 30º to the horizontal. A body of
mass 2kg is released from the top of the slope and travels down the slope against a
constant resistance. The body reaches the bottom of the slope with speed 2 m/s.
Find the work done against the resistance.

A string, with one end fixed, passes under a
movable pulley of mass 8 kg, and over a fixed
pulley; the string carries a 5 kg mass at its other
end. Find the acceleration of the 5 kg mass.

Suppose, you live in a place on the equator. There is a vertical rod of length 2m on
your roof top. One morning, you went to the roof top and observed the shadow of the
rod. If the length of the rod was 1m, then what time was that?