Câu 9:
Trọng lượng của vật: $P=10m=10.2-20N$
Câu 10:
a, $S_{MN}=v_{1}.t_{1}=10.1,5=15km$
b, $S_{NP}=v_{2}.t_{2}=12.2,5=30km$
$⇒S_{MNP}=S_{MN}+S_{NP}=30+15=45km$
c, $v_{tb}=\dfrac{S_{MNP}}{t_{1}+t_{2}}=\dfrac{45}{1,5+2,5}=11,25km/h$
Câu 11:
a, $p_{A}=d_{n}.(h-0,5)=10000.(2-0,5)=15000Pa$
b, $p=d_{n}.h=10000.2=20000Pa$
Câu 12:
a, $F_{A}=18-12=6N$
b, $F_{A}=V.d_{n}$
$⇒V=\dfrac{F_{A}}{d_{n}}=\dfrac{6}{10000}=6.10^{-4}m³$
c, $D_{v}=\dfrac{m}{V}=\dfrac{\dfrac{P}{10}}{V}=\dfrac{\dfrac{18}{10}}{6.10^{-4}}=3000kg/m³$
