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physics.fisikastudycenter.com - Learning 5 Common problems of material density, grade 7 of yunior high school physics.

Density
The density of a material is equal to its mass divided by its volume:

where:
ρ = density in kg/m³
m = mass in kg
V = volume in m³

Problem 1
A body of 300 g with a volume of 400 cm³. Find the density of the body show your answer in kg/m³!

Answer
The data:
m = 300 g
V = 400 cm³

So then :
ρ = m/V = 300 / 400 = 0.75 g/cm³
ρ = 0.75 x 1000 = 750 kg/m³

Problem 2
A block of a density of 700 kg/m³ has 2 kg of mass. Find the the volume of the block show in cm³ and liter!

Answer
The data:
m = 2 kg
ρ = 700 kg/m³

So then:
V = m / ρ
V = 2 / 2000 m³
V = (2/2000) x 1000000 cm³ = 1000 cm³
in liter
V = 1000 cm³ = 1dm³ = 1 liter

Problem 3
A block with its lenght, widht and height are 20 cm, 5 cm and 6 cm respectively. Find mass of the block when its density is 0.8 g/cm³!


Answer
First find the volume:
V = p x l x t = 20 cm x 5 cm x 6 cm = 600 cm³
So then the mass of the block m = ρ x V = 0,8 x 600 = 480 gram

Problem 4
An experiment to measure the densty of a body using below equipment.

From the data you get, find the density of the body note that the mass of the body is 300 gram!

Answer
Data:
Volume V = 300 ml = 300 cm ³ (terlihat dari gelas ukur)
Mass m = 300 gram
So then:
ρ = m/V = 300 / 300 = 1 g/cm³

Note:
1 ml = 1 cc = 1 cm³

Problem 5
A student does an experiment to measure the density of a rock using below equipment. What is the density of the rock show in g/cm³!


Answer
m = 300 gram
V = 500 − 300 = 200 ml = 200 cm³
ρ = m/V
ρ = 300 / 200 = 1,5 g/cm³

Problem 6
An experiment below is to measure the density of a material. What is the density of the material?


Answer
Mass measurement shows the mass of the material m = 250 gram
Volume measurement shows the volume of the material V = 500 − 300 = 200 ml = 200 cm³
The density of a material is equal to its mass divided by its volume.
So then:
ρ = m / V
ρ = 250 / 200 = 1,25 g/cm³