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GRADE 7 PRACTICE

Physics Problems: Mass and density, Grade 7

Inertia, mass, volume and density of matter.

18 problems across 4 sub-topics
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Problem statements

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18 problems
Position in this set: 1 from 18

Problem #19

Inertia, interaction and mass

What concept does the description correspond to: “The persistence of an object's velocity when external actions are absent or balance one another.»?

Answer options

  1. \text{Inertia}
  2. \text{Interaction between objects}
  3. \text{Mass}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{The persistence of an object's velocity when external actions are absent or balance one another.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    A trolley does not instantly stop by itself: friction and air resistance change its velocity.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Inertia}

Answer\text{Concept} = \text{Inertia}

Position in this set: 2 from 18

Problem #20

Inertia, interaction and mass

What concept does the description correspond to: “In an interaction, each object acts on the other and may change its velocity or shape.»?

Answer options

  1. \text{Interaction between objects}
  2. \text{Inertia}
  3. \text{Mass}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{In an interaction, each object acts on the other and may change its velocity or shape.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    After a collision, both trolleys change their motion, though the changes may differ because their masses differ.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Interaction between objects}

Answer\text{Concept} = \text{Interaction between objects}

Position in this set: 3 from 18

Problem #21

Mass and inertia

Two free carts are subjected to equal forces for the same amount of time. The first one changed the speed less. Which conclusion is correct?

Answer options

  1. \text{Mass first carts more}
  2. \text{Mass first carts less}
  3. \text{Masses necessarily equal}
  4. \text{First trolley not has inertia}
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Given
F_1
F_2
t_1
t_2
Find

\text{comparison masses}

  1. \text{When the same influence more inert body changes speed less}
  2. \text{Big inertia corresponds greater mass}m_1>m_2

Answerm_1>m_2

Position in this set: 4 from 18

Problem #22

Volume and density

What concept does the description correspond to: “A physical quantity that measures the space occupied by an object or substance.»?

Answer options

  1. \text{Volume}
  2. \text{Density table}
  3. \text{Density}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{A physical quantity that measures the space occupied by an object or substance.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    Find a rectangular block's volume from its dimensions and an irregular object's volume from the liquid it displaces.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Volume}

Answer\text{Concept} = \text{Volume}

Position in this set: 5 from 18

Problem #23

Volume and density

What concept does the description correspond to: “A reference table lists substances and their densities at specified temperatures and states of matter.»?

Answer options

  1. \text{Density table}
  2. \text{Volume}
  3. \text{Density}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{A reference table lists substances and their densities at specified temperatures and states of matter.}
Find

\text{name concepts}

  1. \text{Let's compare approval with definition}

    Before using the table, express mass and volume in compatible units and check the substance's state of matter.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Density table}

Answer\text{Concept} = \text{Density table}

Position in this set: 6 from 18

Problem #24

Density

The mass of a homogeneous part is 540 g, and its volume is 200 cm³. Find the density of the part.

Answer options

  1. 2{,}7\,\text{г/см}^{3}
  2. 0{,}37\,\text{г/см}^{3}
  3. 108\,\text{г/см}^{3}
  4. 740\,\text{г/см}^{3}
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Given
m
540\,\text{г}
V
200\,\text{см}^{3}
Find

\rho

  1. \rho=\frac{m}{V}\rho=\frac{540}{200}\,\text{г/см}^{3}\rho = 2{,}7\,\text{г/см}^{3}

Answer2{,}7\,\text{г/см}^{3}

Position in this set: 7 from 18

Problem #94

Inertia, interaction and mass

Body balanced weights by the masses 200 and 50 g on equal-armed scales. Find mass body.

Answer options

  1. 250\,\text{г}
  2. 500\,\text{г}
  3. 125\,\text{г}
  4. 750\,\text{г}
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Given
m_1
200\,\text{г}
m_2
50\,\text{г}
Find

m

  1. m=m_1+m_2m=200 + 50m=250\,\text{г}

    In equilibrium of equal-armed scales, the masses on the cups are equal.

Answer250\,\text{г}

Position in this set: 8 from 18

Problem #95

Inertia, interaction and mass

Body balanced weights by the masses 500 and 100 g on equal-armed scales. Find mass body.

Answer options

  1. 1200\,\text{г}
  2. 600\,\text{г}
  3. 300\,\text{г}
  4. 1800\,\text{г}
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Given
m_1
500\,\text{г}
m_2
100\,\text{г}
Find

m

  1. m=m_1+m_2m=500 + 100m=600\,\text{г}

    In equilibrium of equal-armed scales, the masses on the cups are equal.

Answer600\,\text{г}

Position in this set: 9 from 18

Problem #96

Inertia, interaction and mass

Box mass 100 g with 8 identical details has mass 500 g. Find mass one details.

Answer options

  1. 100\,\text{г}
  2. 50\,\text{г}
  3. 25\,\text{г}
  4. 150\,\text{г}
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Given
m_0
100\,\text{г}
n
8\,\text{деталей}
M
500\,\text{г}
Find

a

  1. m=M-m_0m=500 - 100m=400\,\text{г}

    Subtract the mass of the container.

  2. a=\frac{m}{n}a=\frac{400}{8}a=50\,\text{г}

    We divide the mass of parts by their number.

Answer50\,\text{г}

Position in this set: 10 from 18

Problem #97

Inertia, interaction and mass

Box mass 200 g with 12 identical details has mass 920 g. Find mass one details.

Answer options

  1. 120\,\text{г}
  2. 30\,\text{г}
  3. 60\,\text{г}
  4. 180\,\text{г}
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Given
m_0
200\,\text{г}
n
12\,\text{деталей}
M
920\,\text{г}
Find

a

  1. m=M-m_0m=920 - 200m=720\,\text{г}

    Subtract the mass of the container.

  2. a=\frac{m}{n}a=\frac{720}{12}a=60\,\text{г}

    We divide the mass of parts by their number.

Answer60\,\text{г}

Position in this set: 11 from 18

Problem #98

Inertia, interaction and mass

Box with 10 identical cargo weighs on scales 700 g. Empty box has mass 100 g. From her shifted 4 cargo B another empty box mass 80 g. Find mass second boxes with cargo.

Answer options

  1. 640\,\text{г}
  2. 160\,\text{г}
  3. 320\,\text{г}
  4. 960\,\text{г}
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Given
n
10\,\text{грузов}
M
700\,\text{г}
m_0
100\,\text{г}
k
4\,\text{грузов}
b
80\,\text{г}
Find

R

  1. a=\frac{M-m_0}{n}a=\frac{(700 - 100)}{10}a=60\,\text{г}

    First, we find the mass of one load without containers.

  2. m=akm=60 \cdot 4m=240\,\text{г}

    Weight is maintained when carrying loads.

  3. R=b+mR=80 + 240R=320\,\text{г}

    Add the mass of the second box.

Answer320\,\text{г}

Position in this set: 12 from 18

Problem #99

Inertia, interaction and mass

Box with 12 identical cargo weighs on scales 1060 g. Empty box has mass 100 g. From her shifted 5 cargo B another empty box mass 120 g. Find mass second boxes with cargo.

Answer options

  1. 1040\,\text{г}
  2. 260\,\text{г}
  3. 1560\,\text{г}
  4. 520\,\text{г}
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Given
n
12\,\text{грузов}
M
1060\,\text{г}
m_0
100\,\text{г}
k
5\,\text{грузов}
b
120\,\text{г}
Find

R

  1. a=\frac{M-m_0}{n}a=\frac{(1060 - 100)}{12}a=80\,\text{г}

    First, we find the mass of one load without containers.

  2. m=akm=80 \cdot 5m=400\,\text{г}

    Weight is maintained when carrying loads.

  3. R=b+mR=120 + 400R=520\,\text{г}

    Add the mass of the second box.

Answer520\,\text{г}

Position in this set: 13 from 18

Problem #100

Volume and density

Volume details 20 cm³, density material 2{,}7 g/cm³. Find mass details.

Answer options

  1. 108\,\text{г}
  2. 54\,\text{г}
  3. 27\,\text{г}
  4. 162\,\text{г}
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Given
V
20\,\text{см}^{3}
r
2{,}7\,\text{г/см}^{3}
Find

m

  1. m=\rho Vm=2{,}7 \cdot 20m=54\,\text{г}

    Density and volume are given in consistent units.

Answer54\,\text{г}

Position in this set: 14 from 18

Problem #101

Volume and density

Volume details 30 cm³, density material 7{,}8 g/cm³. Find mass details.

Answer options

  1. 468\,\text{г}
  2. 117\,\text{г}
  3. 234\,\text{г}
  4. 702\,\text{г}
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Given
V
30\,\text{см}^{3}
r
7{,}8\,\text{г/см}^{3}
Find

m

  1. m=\rho Vm=7{,}8 \cdot 30m=234\,\text{г}

    Density and volume are given in consistent units.

Answer234\,\text{г}

Position in this set: 15 from 18

Problem #102

Volume and density

After dives body mass 156 g level water B beaker grew up with 40 up to 60 ml. Find density body B g/cm³.

Answer options

  1. 15{,}6\,\text{г/см}^{3}
  2. 3{,}9\,\text{г/см}^{3}
  3. 7{,}8\,\text{г/см}^{3}
  4. 23{,}4\,\text{г/см}^{3}
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Given
m
156\,\text{г}
V_1
40\,\text{мл}
V_2
60\,\text{мл}
Find

\rho

  1. V=V_2-V_1V=60 - 40V=20\,\text{см}^{3}

    One milliliter is equal to one cubic centimeter.

  2. \rho=\frac{m}{V}\rho=\frac{156}{20}\rho=7{,}8\,\text{г/см}^{3}

    Divide the mass by the volume of the body.

Answer7{,}8\,\text{г/см}^{3}

Position in this set: 16 from 18

Problem #103

Volume and density

After dives body mass 270 g level water B beaker grew up with 50 up to 150 ml. Find density body B g/cm³.

Answer options

  1. 5{,}4\,\text{г/см}^{3}
  2. 1{,}35\,\text{г/см}^{3}
  3. 8{,}1\,\text{г/см}^{3}
  4. 2{,}7\,\text{г/см}^{3}
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Given
m
270\,\text{г}
V_1
50\,\text{мл}
V_2
150\,\text{мл}
Find

\rho

  1. V=V_2-V_1V=150 - 50V=100\,\text{см}^{3}

    One milliliter is equal to one cubic centimeter.

  2. \rho=\frac{m}{V}\rho=\frac{270}{100}\rho=2{,}7\,\text{г/см}^{3}

    Divide the mass by the volume of the body.

Answer2{,}7\,\text{г/см}^{3}

Position in this set: 17 from 18

Problem #104

Volume and density

Detail from material density 2{,}7 g/cm³ has external volume 100 cm³ and mass 216 g. Find volume internal cavities.

Answer options

  1. 40\,\text{см}^{3}
  2. 10\,\text{см}^{3}
  3. 60\,\text{см}^{3}
  4. 20\,\text{см}^{3}
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Given
r
2{,}7\,\text{г/см}^{3}
V
100\,\text{см}^{3}
m
216\,\text{г}
Find

V_{\text{пол}}

  1. V_{\text{мат}}=\frac{m}{\rho}V_{\text{мат}}=\frac{216}{2{,}7}V_{\text{мат}}=80\,\text{см}^{3}

    The weight is due only to the material of the part.

  2. V_{\text{пол}}=V-V_{\text{мат}}V_{\text{пол}}=100 - 80V_{\text{пол}}=20\,\text{см}^{3}

    Subtract the volume of the material from the external volume.

Answer20\,\text{см}^{3}

Position in this set: 18 from 18

Problem #105

Volume and density

Detail from material density 7{,}8 g/cm³ has external volume 80 cm³ and mass 468 g. Find volume internal cavities.

Answer options

  1. 20\,\text{см}^{3}
  2. 40\,\text{см}^{3}
  3. 10\,\text{см}^{3}
  4. 60\,\text{см}^{3}
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Given
r
7{,}8\,\text{г/см}^{3}
V
80\,\text{см}^{3}
m
468\,\text{г}
Find

V_{\text{пол}}

  1. V_{\text{мат}}=\frac{m}{\rho}V_{\text{мат}}=\frac{468}{7{,}8}V_{\text{мат}}=60\,\text{см}^{3}

    The weight is due only to the material of the part.

  2. V_{\text{пол}}=V-V_{\text{мат}}V_{\text{пол}}=80 - 60V_{\text{пол}}=20\,\text{см}^{3}

    Subtract the volume of the material from the external volume.

Answer20\,\text{см}^{3}

The theory behind these problems

Work through the topic if a problem will not give in.

Inertia, interaction and massWhy velocity does not change instantly, and how we compare the masses of objects.Volume and densityDefine density and use it to calculate mass or volume.

Formulas by topic

Look up symbols and units of measurement in the reference.

Massm · кгDensityρ · кг/м³