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GRADE 7 PRACTICE

Physics Problems: Mechanical motion, Grade 7

Frame of reference, path, speed, graphs and acceleration.

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 #13

Reference frame, trajectory and distance travelled

What concept does the description correspond to: “A change in an object's position relative to a chosen reference object as time passes.»?

Answer options

  1. \text{Mechanical motion}
  2. \text{Reference frame}
  3. \text{Trajectory and distance travelled}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{A change in an object's position relative to a chosen reference object as time passes.}
Find

\text{name concepts}

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

    A passenger is at rest relative to the seat, but moves relative to the road. Motion is therefore always described relative to something.

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

Answer\text{Concept} = \text{Mechanical motion}

Position in this set: 2 from 18

Problem #14

Reference frame, trajectory and distance travelled

What concept does the description correspond to: “A reference object, coordinates and a way of measuring time together provide a system for describing motion.»?

Answer options

  1. \text{Reference frame}
  2. \text{Mechanical motion}
  3. \text{Trajectory and distance travelled}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{A reference object, coordinates and a way of measuring time together provide a system for describing motion.}
Find

\text{name concepts}

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

    Choosing the platform or a moving carriage as the reference object can change the velocity we find and the shape of the trajectory.

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

Answer\text{Concept} = \text{Reference frame}

Position in this set: 3 from 18

Problem #15

Mechanical motion

A passenger sits on a uniformly moving bus. Relative to which object is the passenger at rest?

Answer options

  1. \text{Regarding seats}
  2. \text{Regarding roads}
  3. \text{Regarding roadside tree}
  4. \text{Regarding oncoming car}
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Given
\text{passenger}
\text{sitting B on the bus}
Find

\text{body countdown peace}

  1. \text{Let's compare Position passenger with everyone object}
  2. \text{Distance up to seats not is changing}\text{peace relatively seats}

Answer\text{seat}

Position in this set: 4 from 18

Problem #16

Speed, average speed and graphs

What concept does the description correspond to: “When speed changes, average speed is the total distance travelled divided by the total time.»?

Answer options

  1. \text{Motion at changing speed}
  2. \text{Motion at constant speed}
  3. \text{Acceleration}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{When speed changes, average speed is the total distance travelled divided by the total time.}
Find

\text{name concepts}

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

    The average speed need not match the speed on any particular section. It includes even the time spent stopped.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Motion at changing speed}

Answer\text{Concept} = \text{Motion at changing speed}

Position in this set: 5 from 18

Problem #17

Speed, average speed and graphs

What concept does the description correspond to: “Motion has constant speed if the object covers equal distances in any equal time intervals.»?

Answer options

  1. \text{Motion at constant speed}
  2. \text{Motion at changing speed}
  3. \text{Acceleration}
  4. \text{Physical phenomenon}
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Given
\text{Description}
\text{Motion has constant speed if the object covers equal distances in any equal time intervals.}
Find

\text{name concepts}

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

    On a distance–time graph, constant speed gives a straight line whose slope tells us the speed.

  2. \text{Let's formulate conclusion}\text{Concept} = \text{Motion at constant speed}

Answer\text{Concept} = \text{Motion at constant speed}

Position in this set: 6 from 18

Problem #18

Velocity

A cyclist travels 600 m in 2 minutes at a constant speed. Find the speed in SI units.

Answer options

  1. 5\,\text{м/с}
  2. 3\,\text{м/с}
  3. 10\,\text{м/с}
  4. 300\,\text{м/с}
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Given
s
600\,\text{м}
t
2\,\text{мин}120\,\text{с}
Find

v

  1. v=\frac{s}{t}v=\frac{600}{120}\,\text{м/с}v = 5\,\text{м/с}

Answer5\,\text{м/с}

Position in this set: 7 from 18

Problem #82

Reference frame, trajectory and distance travelled

A cyclist moves uniformly at a speed 4 m/s for 30 s. Find the path you have taken.

Answer options

  1. 120\,\text{м}
  2. 240\,\text{м}
  3. 60\,\text{м}
  4. 360\,\text{м}
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Given
v
4\,\text{м/с}
t
30\,\text{с}
Find

S

  1. S=vtS=4 \cdot 30S=120\,\text{м}

    In uniform motion, the path is equal to the product of speed and time.

Answer120\,\text{м}

Position in this set: 8 from 18

Problem #83

Reference frame, trajectory and distance travelled

A cyclist moves uniformly at a speed 6 m/s for 40 s. Find the path you have taken.

Answer options

  1. 480\,\text{м}
  2. 240\,\text{м}
  3. 120\,\text{м}
  4. 720\,\text{м}
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Given
v
6\,\text{м/с}
t
40\,\text{с}
Find

S

  1. S=vtS=6 \cdot 40S=240\,\text{м}

    In uniform motion, the path is equal to the product of speed and time.

Answer240\,\text{м}

Position in this set: 9 from 18

Problem #84

Reference frame, trajectory and distance travelled

The tourist passed 300 m to the east, then 100 m to the west. Took all the way 200 s. Find the average ground speed.

Answer options

  1. 4\,\text{м/с}
  2. 2\,\text{м/с}
  3. 1\,\text{м/с}
  4. 6\,\text{м/с}
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Given
a
300\,\text{м}
b
100\,\text{м}
t
200\,\text{с}
Find

v

  1. S=a+bS=300 + 100S=400\,\text{м}

    We add up the path regardless of the direction of movement.

  2. v=\frac{S}{t}v=\frac{400}{200}v=2\,\text{м/с}

    Average ground speed uses the entire path rather than travel.

Answer2\,\text{м/с}

Position in this set: 10 from 18

Problem #85

Reference frame, trajectory and distance travelled

The tourist passed 450 m to the east, then 150 m to the west. Took all the way 240 s. Find the average ground speed.

Answer options

  1. 5\,\text{м/с}
  2. 1{,}25\,\text{м/с}
  3. 2{,}5\,\text{м/с}
  4. 7{,}5\,\text{м/с}
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Given
a
450\,\text{м}
b
150\,\text{м}
t
240\,\text{с}
Find

v

  1. S=a+bS=450 + 150S=600\,\text{м}

    We add up the path regardless of the direction of movement.

  2. v=\frac{S}{t}v=\frac{600}{240}v=2{,}5\,\text{м/с}

    Average ground speed uses the entire path rather than travel.

Answer2{,}5\,\text{м/с}

Position in this set: 11 from 18

Problem #86

Reference frame, trajectory and distance travelled

The tourist passed 240 m at speed 2 m/s, resting 60 s and passed some more 360 m at speed 3 m/s. Find the average speed over the entire time.

Answer options

  1. 4\,\text{м/с}
  2. 1\,\text{м/с}
  3. 2\,\text{м/с}
  4. 6\,\text{м/с}
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Given
a
240\,\text{м}
b
360\,\text{м}
v_1
2\,\text{м/с}
v_2
3\,\text{м/с}
t_0
60\,\text{с}
Find

v

  1. t_1=\frac{a}{v_1}t_1=\frac{240}{2}t_1=120\,\text{с}

    We find the time of the first section.

  2. t_2=\frac{b}{v_2}t_2=\frac{360}{3}t_2=120\,\text{с}

    Finding the time for the second section.

  3. T=t_1+t_0+t_2T=120 + 60 + 120T=300\,\text{с}

    The stop is included in the total time.

  4. v=\frac{a+b}{T}v=\frac{(240 + 360)}{300}v=2\,\text{м/с}

    We divide the total path by the total time.

Answer2\,\text{м/с}

Position in this set: 12 from 18

Problem #87

Reference frame, trajectory and distance travelled

The tourist passed 360 m at speed 3 m/s, resting 60 s and passed some more 540 m at speed 4{,}5 m/s. Find the average speed over the entire time.

Answer options

  1. 6\,\text{м/с}
  2. 1{,}5\,\text{м/с}
  3. 9\,\text{м/с}
  4. 3\,\text{м/с}
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Given
a
360\,\text{м}
b
540\,\text{м}
v_1
3\,\text{м/с}
v_2
4{,}5\,\text{м/с}
t_0
60\,\text{с}
Find

v

  1. t_1=\frac{a}{v_1}t_1=\frac{360}{3}t_1=120\,\text{с}

    We find the time of the first section.

  2. t_2=\frac{b}{v_2}t_2=\frac{540}{4{,}5}t_2=120\,\text{с}

    Finding the time for the second section.

  3. T=t_1+t_0+t_2T=120 + 60 + 120T=300\,\text{с}

    The stop is included in the total time.

  4. v=\frac{a+b}{T}v=\frac{(360 + 540)}{300}v=3\,\text{м/с}

    We divide the total path by the total time.

Answer3\,\text{м/с}

Position in this set: 13 from 18

Problem #88

Speed, average speed and graphs

On graphics uniform movement for 20 with way grew up from zero up to 100 m. Find speed.

Answer options

  1. 10\,\text{м/с}
  2. 5\,\text{м/с}
  3. 2{,}5\,\text{м/с}
  4. 15\,\text{м/с}
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Given
t
20\,\text{с}
S
100\,\text{м}
Find

v

  1. v=\frac{S}{t}v=\frac{100}{20}v=5\,\text{м/с}

    Speed is equal to the slope of the graph of the path to the time axis.

Answer5\,\text{м/с}

Position in this set: 14 from 18

Problem #89

Speed, average speed and graphs

On graphics uniform movement for 30 with way grew up from zero up to 210 m. Find speed.

Answer options

  1. 14\,\text{м/с}
  2. 3{,}5\,\text{м/с}
  3. 7\,\text{м/с}
  4. 21\,\text{м/с}
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Given
t
30\,\text{с}
S
210\,\text{м}
Find

v

  1. v=\frac{S}{t}v=\frac{210}{30}v=7\,\text{м/с}

    Speed is equal to the slope of the graph of the path to the time axis.

Answer7\,\text{м/с}

Position in this set: 15 from 18

Problem #90

Speed, average speed and graphs

The car is moving at speed 54 km/h. Which way B meters he will pass for 20 with?

Answer options

  1. 600\,\text{м}
  2. 150\,\text{м}
  3. 300\,\text{м}
  4. 900\,\text{м}
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Given
v
54\,\text{км/ч}
t
20\,\text{с}
Find

S

  1. u=\frac{v}{3{,}6}u=\frac{54}{3{,}6}u=15\,\text{м/с}

    Convert km/h to m/s.

  2. S=utS=15 \cdot 20S=300\,\text{м}

    Speed and time are now given in consistent units.

Answer300\,\text{м}

Position in this set: 16 from 18

Problem #91

Speed, average speed and graphs

The car is moving at speed 72 km/h. Which way B meters he will pass for 30 with?

Answer options

  1. 1200\,\text{м}
  2. 300\,\text{м}
  3. 1800\,\text{м}
  4. 600\,\text{м}
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Given
v
72\,\text{км/ч}
t
30\,\text{с}
Find

S

  1. u=\frac{v}{3{,}6}u=\frac{72}{3{,}6}u=20\,\text{м/с}

    Convert km/h to m/s.

  2. S=utS=20 \cdot 30S=600\,\text{м}

    Speed and time are now given in consistent units.

Answer600\,\text{м}

Position in this set: 17 from 18

Problem #92

Speed, average speed and graphs

first half ways length 600 m cyclist passed at speed 3 m/s, second half at speed 6 m/s. Here 600 m, this is length total ways. Find average speed.

Answer options

  1. 8\,\text{м/с}
  2. 2\,\text{м/с}
  3. 12\,\text{м/с}
  4. 4\,\text{м/с}
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Given
S
600\,\text{м}
v_1
3\,\text{м/с}
v_2
6\,\text{м/с}
Find

v

  1. t_1=\frac{S}{2v_1}t_1=\frac{\frac{600}{2}}{3}t_1=100\,\text{с}

    Equal paths do not mean equal times.

  2. t_2=\frac{S}{2v_2}t_2=\frac{\frac{600}{2}}{6}t_2=50\,\text{с}

    We calculate the time of the second half separately.

  3. v=\frac{S}{t_1+t_2}v=\frac{600}{(100 + 50)}v=4\,\text{м/с}

    This calculation cannot be replaced by the arithmetic average of speeds.

Answer4\,\text{м/с}

Position in this set: 18 from 18

Problem #93

Speed, average speed and graphs

first half ways length 1200 m cyclist passed at speed 4 m/s, second half at speed 12 m/s. Here 1200 m, this is length total ways. Find average speed.

Answer options

  1. 6\,\text{м/с}
  2. 12\,\text{м/с}
  3. 3\,\text{м/с}
  4. 18\,\text{м/с}
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Given
S
1200\,\text{м}
v_1
4\,\text{м/с}
v_2
12\,\text{м/с}
Find

v

  1. t_1=\frac{S}{2v_1}t_1=\frac{\frac{1200}{2}}{4}t_1=150\,\text{с}

    Equal paths do not mean equal times.

  2. t_2=\frac{S}{2v_2}t_2=\frac{\frac{1200}{2}}{12}t_2=50\,\text{с}

    We calculate the time of the second half separately.

  3. v=\frac{S}{t_1+t_2}v=\frac{1200}{(150 + 50)}v=6\,\text{м/с}

    This calculation cannot be replaced by the arithmetic average of speeds.

Answer6\,\text{м/с}

The theory behind these problems

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

Reference frame, trajectory and distance travelledHow motion depends on the reference frame, and how to describe an object's position.Speed, average speed and graphsMotion at constant and changing speeds, motion equations, and an introduction to acceleration.

Formulas by topic

Look up symbols and units of measurement in the reference.

Timet, τ · сDistance and pathS, l · мVelocityv · м/сAccelerationa · м/с²