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GRADE 7 PRACTICE

Physics Problems: Physics and measurements, Grade 7

Phenomena, experiment, quantities and accuracy of measurements.

18 problems across 4 sub-topics
Practise in the interactive mode

Here the conditions and analysis of the solution can be read without an account. In the simulator, you need to collect the same analyzes yourself: “Given,” formulas, order of steps and answer.

Problem statements

The answer options are there to check against, and the walkthrough opens under each problem.

18 problems
Position in this set: 1 from 18

Problem #1

Physical phenomena and how we investigate them

What concept does the description correspond to: “A change that occurs in a body or substance and is observable or measurable.»?

Answer options

  1. \text{Physical phenomenon}
  2. \text{Objects, substances and physical reality}
  3. \text{Observation and experiment}
  4. \text{Physical quantity}
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Given
\text{Description}
\text{A change that occurs in a body or substance and is observable or measurable.}
Find

\text{name concepts}

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

    Mechanical, thermal, electrical, magnetic, light and sound phenomena differ in characteristics, but are studied by a common scientific method.

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

Answer\text{Concept} = \text{Physical phenomenon}

Position in this set: 2 from 18

Problem #2

Physical phenomena and how we investigate them

What concept does the description correspond to: “A physical object is a distinct item; substances make up objects. Physical reality includes everything that exists physically, including substances and fields.»?

Answer options

  1. \text{Objects, substances and physical reality}
  2. \text{Physical phenomenon}
  3. \text{Observation and experiment}
  4. \text{Physical quantity}
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Given
\text{Description}
\text{A physical object is a distinct item; substances make up objects. Physical reality includes everything that exists physically, including substances and fields.}
Find

\text{name concepts}

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

    A drinking glass is an object, and glass is its material. Both substances and physical fields are part of physical reality.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Objects, substances and physical reality}

Answer\text{Concept} = \text{Objects, substances and physical reality}

Position in this set: 3 from 18

Problem #3

Physics and experiment

The student assumes that the dark surface heats up in the sun faster than the light one. Which action would best test the hypothesis?

Answer options

  1. \text{compare heating dark and light plates identical material and size}
  2. \text{Observe only dark plate}
  3. \text{Ask opinion classmates}
  4. \text{change material and size plates}
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Given
\text{Hypothesis}
\text{color influences on heating}
Find

\text{inspector experience}

  1. \text{We leave identical material, size and lighting}

    Then the only controllable difference is the color of the surface.

  2. \text{We measure both temperature through equal intervals}\text{comparable data}

Answer\text{comparison dark and light plates at the same lighting}

Position in this set: 4 from 18

Problem #4

Measuring instruments and accuracy

What concept does the description correspond to: “A measurable property of a body or phenomenon that is expressed by a number and a chosen unit.»?

Answer options

  1. \text{Physical quantity}
  2. \text{Scale and scale interval}
  3. \text{Accuracy and uncertainty}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{A measurable property of a body or phenomenon that is expressed by a number and a chosen unit.}
Find

\text{name concepts}

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

    Length, time, mass and temperature allow objects to be compared quantitatively, and the SI system makes the results understandable to everyone.

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

Answer\text{Concept} = \text{Physical quantity}

Position in this set: 5 from 18

Problem #5

Measuring instruments and accuracy

What concept does the description correspond to: “A scale is a set of marks on an instrument. The scale interval is the change in the measured quantity between adjacent marks.»?

Answer options

  1. \text{Scale and scale interval}
  2. \text{Physical quantity}
  3. \text{Accuracy and uncertainty}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{A scale is a set of marks on an instrument. The scale interval is the change in the measured quantity between adjacent marks.}
Find

\text{name concepts}

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

    To read an instrument, find two labelled marks and divide the difference between them by the number of intervals; then use that interval to take the reading.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Scale and scale interval}

Answer\text{Concept} = \text{Scale and scale interval}

Position in this set: 6 from 18

Problem #6

measurements

Between the 2 cm and 3 cm marks on the scale there are five identical spaces. What is the price of one division?

Answer options

  1. 2\,\text{мм}
  2. 5\,\text{мм}
  3. 0{,}5\,\text{мм}
  4. 10\,\text{мм}
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Given
x_1
2\,\text{см}
x_2
3\,\text{см}
n
5
Find

c

  1. c=\frac{x_2-x_1}{n}c=\frac{3-2}{5}\,\text{см}c = 0{,}2\,\text{см}
  2. 1\,\text{см}=10\,\text{мм}c=2\,\text{мм}

Answer2\,\text{мм}

Position in this set: 7 from 18

Problem #58

Physical phenomena and how we investigate them

Observation started on mark 15 with and it's over on mark 75 with stopwatch. How much seconds it continued?

Answer options

  1. 60\,\text{с}
  2. 120\,\text{с}
  3. 30\,\text{с}
  4. 180\,\text{с}
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Given
t_1
15\,\text{с}
t_2
75\,\text{с}
Find

t

  1. t=t_2-t_1t=75 - 15t=60\,\text{с}

    The duration is equal to the difference in readings, not the final reading.

Answer60\,\text{с}

Position in this set: 8 from 18

Problem #59

Physical phenomena and how we investigate them

Observation started on mark 25 with and it's over on mark 115 with stopwatch. How much seconds it continued?

Answer options

  1. 180\,\text{с}
  2. 90\,\text{с}
  3. 45\,\text{с}
  4. 270\,\text{с}
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Given
t_1
25\,\text{с}
t_2
115\,\text{с}
Find

t

  1. t=t_2-t_1t=115 - 25t=90\,\text{с}

    The duration is equal to the difference in readings, not the final reading.

Answer90\,\text{с}

Position in this set: 9 from 18

Problem #60

Physical phenomena and how we investigate them

B three identical experiments time melting ice amounted to 110, 120 and 130 s. Find Average time.

Answer options

  1. 240\,\text{с}
  2. 120\,\text{с}
  3. 60\,\text{с}
  4. 360\,\text{с}
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Given
t_1
110\,\text{с}
t_2
120\,\text{с}
t_3
130\,\text{с}
Find

t

  1. S=t_1+t_2+t_3S=110 + 120 + 130S=360\,\text{с}

    We add up the results of repeated measurements.

  2. t=\frac{S}{3}t=\frac{360}{3}t=120\,\text{с}

    Divide the amount by the number of experiments.

Answer120\,\text{с}

Position in this set: 10 from 18

Problem #61

Physical phenomena and how we investigate them

B three identical experiments time melting ice amounted to 170, 180 and 190 s. Find Average time.

Answer options

  1. 360\,\text{с}
  2. 90\,\text{с}
  3. 180\,\text{с}
  4. 540\,\text{с}
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Given
t_1
170\,\text{с}
t_2
180\,\text{с}
t_3
190\,\text{с}
Find

t

  1. S=t_1+t_2+t_3S=170 + 180 + 190S=540\,\text{с}

    We add up the results of repeated measurements.

  2. t=\frac{S}{3}t=\frac{540}{3}t=180\,\text{с}

    Divide the amount by the number of experiments.

Answer180\,\text{с}

Position in this set: 11 from 18

Problem #62

Physical phenomena and how we investigate them

When the same lighting dark plate got hot from 20 up to 44 °C, light from 21 up to 36 °C. On how much degrees increase temperature dark plates more? material, dimensions and duration experiments are the same.

Answer options

  1. 18\,\text{°C}
  2. 4{,}5\,\text{°C}
  3. 9\,\text{°C}
  4. 27\,\text{°C}
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Given
T_1
20\,\text{°C}
T_2
44\,\text{°C}
T_3
21\,\text{°C}
T_4
36\,\text{°C}
Find

d

  1. \Delta T_1=T_2-T_1\Delta T_1=44 - 20\Delta T_1=24\,\text{°C}

    For each plate, we take into account its initial temperature.

  2. \Delta T_2=T_4-T_3\Delta T_2=36 - 21\Delta T_2=15\,\text{°C}

    We find the increase for the light plate.

  3. d=\Delta T_1-\Delta T_2d=24 - 15d=9\,\text{°C}

    We compare increments, not final temperatures.

Answer9\,\text{°C}

Position in this set: 12 from 18

Problem #63

Physical phenomena and how we investigate them

When the same lighting dark plate got hot from 22 up to 52 °C, light from 23 up to 41 °C. On how much degrees increase temperature dark plates more? material, dimensions and duration experiments are the same.

Answer options

  1. 24\,\text{°C}
  2. 6\,\text{°C}
  3. 36\,\text{°C}
  4. 12\,\text{°C}
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Given
T_1
22\,\text{°C}
T_2
52\,\text{°C}
T_3
23\,\text{°C}
T_4
41\,\text{°C}
Find

d

  1. \Delta T_1=T_2-T_1\Delta T_1=52 - 22\Delta T_1=30\,\text{°C}

    For each plate, we take into account its initial temperature.

  2. \Delta T_2=T_4-T_3\Delta T_2=41 - 23\Delta T_2=18\,\text{°C}

    We find the increase for the light plate.

  3. d=\Delta T_1-\Delta T_2d=30 - 18d=12\,\text{°C}

    We compare increments, not final temperatures.

Answer12\,\text{°C}

Position in this set: 13 from 18

Problem #64

Measuring instruments and accuracy

Between marks 20 and 60 ml beakers 8 equal gaps. Find price divisions.

Answer options

  1. 10\,\text{мл}
  2. 5\,\text{мл}
  3. 2{,}5\,\text{мл}
  4. 15\,\text{мл}
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Given
a
20\,\text{мл}
b
60\,\text{мл}
n
8\,\text{делений}
Find

c

  1. c=\frac{b-a}{n}c=\frac{(60 - 20)}{8}c=5\,\text{мл}

    We count the spaces between strokes.

Answer5\,\text{мл}

Position in this set: 14 from 18

Problem #65

Measuring instruments and accuracy

Between marks 40 and 100 ml beakers 12 equal gaps. Find price divisions.

Answer options

  1. 10\,\text{мл}
  2. 2{,}5\,\text{мл}
  3. 5\,\text{мл}
  4. 15\,\text{мл}
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Given
a
40\,\text{мл}
b
100\,\text{мл}
n
12\,\text{делений}
Find

c

  1. c=\frac{b-a}{n}c=\frac{(100 - 40)}{12}c=5\,\text{мл}

    We count the spaces between strokes.

Answer5\,\text{мл}

Position in this set: 15 from 18

Problem #66

Measuring instruments and accuracy

After additions 40 identical drops indication beakers has grown with 10 up to 12 ml. Find Volume of one drop.

Answer options

  1. 0{,}1\,\text{мл}
  2. 0{,}025\,\text{мл}
  3. 0{,}05\,\text{мл}
  4. 0{,}15\,\text{мл}
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Given
n
40\,\text{капель}
V_1
10\,\text{мл}
V_2
12\,\text{мл}
Find

v

  1. V=V_2-V_1V=12 - 10V=2\,\text{мл}

    Find the volume of all added drops.

  2. v=\frac{V}{n}v=\frac{2}{40}v=0{,}05\,\text{мл}

    Divide the total volume by the number of identical drops.

Answer0{,}05\,\text{мл}

Position in this set: 16 from 18

Problem #67

Measuring instruments and accuracy

After additions 50 identical drops indication beakers has grown with 15 up to 19 ml. Find Volume of one drop.

Answer options

  1. 0{,}16\,\text{мл}
  2. 0{,}04\,\text{мл}
  3. 0{,}24\,\text{мл}
  4. 0{,}08\,\text{мл}
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Given
n
50\,\text{капель}
V_1
15\,\text{мл}
V_2
19\,\text{мл}
Find

v

  1. V=V_2-V_1V=19 - 15V=4\,\text{мл}

    Find the volume of all added drops.

  2. v=\frac{V}{n}v=\frac{4}{50}v=0{,}08\,\text{мл}

    Divide the total volume by the number of identical drops.

Answer0{,}08\,\text{мл}

Position in this set: 17 from 18

Problem #68

Measuring instruments and accuracy

Stack from 100 identical sheets has thickness 12 mm. Find thickness one pages B micrometers and then thickness stacks from 250 such sheets B mm. B answer Specify only thickness new stacks.

Answer options

  1. 60\,\text{мм}
  2. 15\,\text{мм}
  3. 90\,\text{мм}
  4. 30\,\text{мм}
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Given
n
100\,\text{листов}
h
12\,\text{мм}
N
250\,\text{листов}
Find

H

  1. d=\frac{h}{n}d=\frac{12}{100}d=0{,}12\,\text{мм}

    Dividing the measured thickness reduces the influence of the ruler division price.

  2. d_{\text{мкм}}=1000d_{\text{мм}}d_{\text{мкм}}=0{,}12 \cdot 1000d_{\text{мкм}}=120\,\text{мкм}

    There are a thousand micrometers in a millimeter.

  3. H=\frac{d_{\text{мкм}}N}{1000}H=\frac{120 \cdot 250}{1000}H=30\,\text{мм}

    Let's go back to millimeters for a new stack.

Answer30\,\text{мм}

Position in this set: 18 from 18

Problem #69

Measuring instruments and accuracy

Stack from 200 identical sheets has thickness 18 mm. Find thickness one pages B micrometers and then thickness stacks from 300 such sheets B mm. B answer Specify only thickness new stacks.

Answer options

  1. 27\,\text{мм}
  2. 54\,\text{мм}
  3. 13{,}5\,\text{мм}
  4. 81\,\text{мм}
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Given
n
200\,\text{листов}
h
18\,\text{мм}
N
300\,\text{листов}
Find

H

  1. d=\frac{h}{n}d=\frac{18}{200}d=0{,}09\,\text{мм}

    Dividing the measured thickness reduces the influence of the ruler division price.

  2. d_{\text{мкм}}=1000d_{\text{мм}}d_{\text{мкм}}=0{,}09 \cdot 1000d_{\text{мкм}}=90\,\text{мкм}

    There are a thousand micrometers in a millimeter.

  3. H=\frac{d_{\text{мкм}}N}{1000}H=\frac{90 \cdot 300}{1000}H=27\,\text{мм}

    Let's go back to millimeters for a new stack.

Answer27\,\text{мм}

The theory behind these problems

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

Physical phenomena and how we investigate themWhat physics studies and how observation turns into a testable experiment.Measuring instruments and accuracySI units, scales, scale intervals, and direct and indirect measurements.