Help on 8'th grade science homework?

Question

A graduated clinder contains 50mL of water. After adding a 30g rock the water in the cylinder reads 75 mL. What is the density of the rock?

Any advice/help?

Thanks! also,

An airplane wing is designed so that air travels __________ (faster, slower) under the wing. This _____________ (increases, decreases) the pressure under the wing, giving the plane lift.

Answer 1

Density = mass / volume

since the volume increases 25 mL, we know the volume of the rocks is 25 mL.

and since we know the rocks weigh 30 g, we can find the density.

D = 30 / 25 = 1.2 g/mL

Answer 2

this is what we call water displacement method in getting the density of an irregular solid... by getting the density we do not follow the formula : D = M/V. so what we do is to subtract the level of the water without the stone from the level of water with the stone. ..
75 - 50 = 25... so the density of the rock is 25 g/mL..
ü

Answer 3

volume of rock= volume of displaced water=25 mL

mass of rock= 30 g

density=mass/volume =30/25=6/5 g/mL =1.2 kg/L (you can play with units whatever you like).

Answer 4

density= mass/volume

30g/25mL= 6/5g per mL

This is my guess...maybe it's not right.

Air would travel slower (the plane is designed for air resistance) and therefore increases the pressure

This is my guess again...I think it's right

Answer 5

15

you subtract what it went up to from what it started at before you put the rock in it

Answer 6

density=20

faster.decreases.

Answer 7

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