A thumb tack has an area of 0.5mm2 in contact with a wall.
A pressure of 40N/mm2
is needed for the drawing pin to go into
the wall.
Calculate the force needed to push the drawing pin into the wall.
Show your working and give the unit with your answer.

In a system, when potential energy decreases, then entropy also decreases. true false

On a day when the barometer reads 75.23 cm, a reaction vessel holds 250 ml of ideal gas at 20 celsius. an oil manometer ( ρ= 810 kg/m^3) reads the pressure in the vessel to be 41 cm of oil and below atmospheric pressure. what volume will the gas occupy under s. t.p.?

The direction of the current in an alternating current circuit remains constant. is direct. changes repeatedly. changes randomly.