The motion of the book is a free fall motion, so it is an uniformly accelerated motion with constant acceleration g=9.8 m/s^2 towards the ground. Therefore we can find the final velocity by using the equation:

$v^2 = u^2 + 2gd$

where

u = 0 is the initial speed

g = 9.8 m/s^2 is the acceleration

d = 10.0 m is the distance covered by the book

Substituting data, we find

$v=\sqrt{0^2 + 2(9.8 m/s^2)(10.0 m)}=14 m/s$

8 0

3 years ago

A balloon filled with helium occupies 20.0 l at 1.50 atm and 25.0◦

bija089 [108]

At stp (standard temperature and pressure), the temperature is T=0 C=273 K and the pressure is p=1.00 atm. So we can use the ideal gas law to find the number of moles of helium:
$pV=nRT$
where p is the pressure (1.00 atm), V the volume (20.0 L), n the number of moles, T the temperature (273 K) and $R=0.082 atm L K^{-1} mol^{-1}$ the gas constant. Using the numbers and re-arranging the formula, we can calculate n:
$n= \frac{pV}{RT}= \frac{(1.00atm)(20.0L)}{(0.082 LatmK^{-1}mol^{-1})(273 K)}=0.89 mol$

5 0

3 years ago