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All questions of Position and Motion for Grade 8 Exam
What is the average velocity of a car that moved 60 km in 3 hours?
- a)60 km/h
- b)20 km/h
- c)30 km/h
- d)10 km/h
Correct answer is option 'B'. Can you explain this answer?
What is the average velocity of a car that moved 60 km in 3 hours?
a)
60 km/h
b)
20 km/h
c)
30 km/h
d)
10 km/h
|
Kamakshi Singh answered |
Calculation of Average Velocity
To calculate the average velocity of a car that moved 60 km in 3 hours, we need to use the formula:
Average Velocity = Total Distance/Total Time
Substituting the given values in the formula, we get:
Average Velocity = 60 km/3 hours
Simplifying this expression, we get:
Average Velocity = 20 km/h
Therefore, the average velocity of the car is 20 km/h.
Explanation
The average velocity of an object is the total distance covered by the object divided by the total time taken to cover that distance. In this case, the car covered a distance of 60 km in a time of 3 hours. Dividing the total distance by the total time gives us the average velocity of the car, which is 20 km/h.
Conclusion
The average velocity of a car that moved 60 km in 3 hours is 20 km/h. It is important to remember that velocity is a vector quantity, which means it has both magnitude and direction. In this case, since no direction is given, we assume that the car travelled in a straight line.
To calculate the average velocity of a car that moved 60 km in 3 hours, we need to use the formula:
Average Velocity = Total Distance/Total Time
Substituting the given values in the formula, we get:
Average Velocity = 60 km/3 hours
Simplifying this expression, we get:
Average Velocity = 20 km/h
Therefore, the average velocity of the car is 20 km/h.
Explanation
The average velocity of an object is the total distance covered by the object divided by the total time taken to cover that distance. In this case, the car covered a distance of 60 km in a time of 3 hours. Dividing the total distance by the total time gives us the average velocity of the car, which is 20 km/h.
Conclusion
The average velocity of a car that moved 60 km in 3 hours is 20 km/h. It is important to remember that velocity is a vector quantity, which means it has both magnitude and direction. In this case, since no direction is given, we assume that the car travelled in a straight line.
The SI unit for speed is- a)km/hour
- b)m/s
- c)cm/min
- d)none of the above
Correct answer is 'B'. Can you explain this answer?
The SI unit for speed is
a)
km/hour
b)
m/s
c)
cm/min
d)
none of the above
|
Shubham Unni answered |
SI unit for speed
The SI unit for speed is meter per second (m/s).
Explanation
Speed is defined as the distance traveled by an object in a given time. It is a scalar quantity and is measured in units of distance per time. The SI unit of distance is meter (m) and the SI unit of time is second (s). Therefore, the SI unit of speed is meter per second (m/s).
For example, if a car travels a distance of 100 meters in 10 seconds, its speed can be calculated as:
Speed = Distance/Time
= 100 meters/10 seconds
= 10 meters per second (m/s)
Therefore, the speed of the car is 10 m/s.
Conclusion
In conclusion, the SI unit for speed is meter per second (m/s). It is important to use the correct units when measuring speed to ensure consistency and accuracy in calculations.
The SI unit for speed is meter per second (m/s).
Explanation
Speed is defined as the distance traveled by an object in a given time. It is a scalar quantity and is measured in units of distance per time. The SI unit of distance is meter (m) and the SI unit of time is second (s). Therefore, the SI unit of speed is meter per second (m/s).
For example, if a car travels a distance of 100 meters in 10 seconds, its speed can be calculated as:
Speed = Distance/Time
= 100 meters/10 seconds
= 10 meters per second (m/s)
Therefore, the speed of the car is 10 m/s.
Conclusion
In conclusion, the SI unit for speed is meter per second (m/s). It is important to use the correct units when measuring speed to ensure consistency and accuracy in calculations.
The SI unit for speed is- a)km/hour
- b)m/s
- c)cm/min
- d)none of the above
Correct answer is option 'B'. Can you explain this answer?
The SI unit for speed is
a)
km/hour
b)
m/s
c)
cm/min
d)
none of the above
|
Prachi Rathore answered |
si unit of speed= si unit of distance/si unit of time =metre/second
1 km/ h = ________ m/s
- a)3/50
- b)18/5
- c)50/3
- d)5/18
Correct answer is option 'D'. Can you explain this answer?
1 km/ h = ________ m/s
a)
3/50
b)
18/5
c)
50/3
d)
5/18
|
Amrutha Mukherjee answered |
Conversion of km/h to m/s
To convert km/h to m/s, we need to use the following conversion factor:
1 km/h = 1000 m/3600 s = 5/18 m/s
So, to convert 1 km/h to m/s, we simply multiply it by 5/18.
Solution
Given, 1 km/h = ?
We need to convert it to m/s.
1 km/h × 5/18 = 5/18 m/s
Therefore, the correct option is (d) 5/18.
To convert km/h to m/s, we need to use the following conversion factor:
1 km/h = 1000 m/3600 s = 5/18 m/s
So, to convert 1 km/h to m/s, we simply multiply it by 5/18.
Solution
Given, 1 km/h = ?
We need to convert it to m/s.
1 km/h × 5/18 = 5/18 m/s
Therefore, the correct option is (d) 5/18.
Which of the following is a correct measure of velocity?
- a)30 s
- b)30 m/s
- c)30 South
- d)30 m/s, South
Correct answer is option 'D'. Can you explain this answer?
Which of the following is a correct measure of velocity?
a)
30 s
b)
30 m/s
c)
30 South
d)
30 m/s, South
|
Pooja Shah answered |
Velocity is a vector quantity, which means it has both magnitude and direction. To correctly measure and describe velocity, you need both these components.
Here’s the analysis of the provided options:
-
30 s: This is a measure of time, not velocity.
-
30 m/s: This is a measure of speed, not velocity, because it does not include a direction.
-
30 South: This describes a direction but lacks the magnitude (speed), so it is not a complete measure of velocity.
-
30 m/s, South: This provides both magnitude (30 m/s) and direction (South), making it a complete measure of velocity.
So, the correct measure of velocity is:
4. 30 m/s, South
How far will a car travel in 25 min at 12 m/s?
- a)24 km
- b)10 km
- c)18 km
- d)14 km
Correct answer is option 'C'. Can you explain this answer?
How far will a car travel in 25 min at 12 m/s?
a)
24 km
b)
10 km
c)
18 km
d)
14 km
|
Molik answered |
S=d/t. .......... t=25min=1500sec. and speed =12m/s.........d=s×t. ...........d=12×1500=18000m. as we hv to convert it into km so 1km=1000m and 1m =1/1000 km so , 18000m=18000/1000km=18km
Speed of 90 km/h when expressed in m/s is- a)2.5
- b)90000
- c)250
- d)25
Correct answer is option 'D'. Can you explain this answer?
Speed of 90 km/h when expressed in m/s is
a)
2.5
b)
90000
c)
250
d)
25
|
Saurabh Kumar answered |
Because when we convert km/h into m/s we multiply 5/18 into km/h so we get m/s according to question we we multiply 5/18 into 90 km/h so90*5/18 = 25SO THE ANSWER IS 25.
Can you explain the answer of this question below:The speed at any instant of time is known as
- A:
velocity
- B:
given speed
- C:
average speed
- D:
instantaneous speed
The answer is d.
The speed at any instant of time is known as
velocity
given speed
average speed
instantaneous speed
|
Gunjan Lakhani answered |
The instantaneous speed of an object is defined as the speed of the object at any given instant. The instantaneous speed of an object can be determined by determining the average speed over a short distance (and short time), and using this approximation as the instantaneous speed.
Topic in NCERT: Motion and Acceleration
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Can you explain the answer of this question below:An object travels 20 m in 5 sec and then another 40 m in 5 sec. What is the average speed of the object?
- A:
6 m/s
- B:
2 m/s
- C:
12 m/s
- D:
0 m/s
The answer is a.
An object travels 20 m in 5 sec and then another 40 m in 5 sec. What is the average speed of the object?
6 m/s
2 m/s
12 m/s
0 m/s
|
Learning Education answered |
Average speed= (Total Distance)/(Total time)
= (20 m + 40 m)/(5 sec + 5 sec)
=60 m/10 sec
=6m/s
Name the instrument used to measure instantaneous speed of a vehicle- a)multimeter
- b)ammeter
- c)speedometer
- d)accelerator
Correct answer is option 'C'. Can you explain this answer?
Name the instrument used to measure instantaneous speed of a vehicle
a)
multimeter
b)
ammeter
c)
speedometer
d)
accelerator
|
|
Anita Menon answered |
The speedometer device is used to measure speed. A speedometer is also called a speedometer, it is a gauge that measures and displays the instantaneous speed of a vehicle.
Can you explain the answer of this question below:If a person walked at 2 m/s for 12 s he/she would travel a distance of
- A:
24 m
- B:
6 m
- C:
4 m
- D:
none of the answers
The answer is a.
If a person walked at 2 m/s for 12 s he/she would travel a distance of
24 m
6 m
4 m
none of the answers
|
Piyush Srivastava answered |
1second =2meter 12 second = 12*2meter 24metet
The area under the speed-time graph gives the ________.- a)velocity
- b)distance
- c)acceleration
- d)time
Correct answer is 'B'. Can you explain this answer?
The area under the speed-time graph gives the ________.
a)
velocity
b)
distance
c)
acceleration
d)
time
|
Trisha Vashisht answered |
Area under the speed-time graph gives the distance:
- When calculating the area under a speed-time graph, you are essentially finding the total distance traveled by an object over a certain period of time.
- This is because the area under a speed-time graph represents the total distance covered by an object as it moves at varying speeds.
- By finding the area under the curve on a speed-time graph, you can determine the total distance traveled by the object during that time interval.
If car A is at 40 km/h and car B is at 10 km/h in the opposite direction, what is the velocity of the car A relative to the car B?
- a)40 km/h
- b)50 km/h.
- c)10 km/h
- d)30 km/h
Correct answer is option 'B'. Can you explain this answer?
If car A is at 40 km/h and car B is at 10 km/h in the opposite direction, what is the velocity of the car A relative to the car B?
a)
40 km/h
b)
50 km/h.
c)
10 km/h
d)
30 km/h
|
Hiral Datta answered |
Taking the formula when both bodies are moving along opposite direction we have :
V(AB) = V(A) - V(B) = 40 - (-10 ) = 50 km/hr
Hence the velocity of car A with respect to car B is 50 km/hr in opposite direction.
How long would it take to travel 50 km traveling at a speed of 10 km/hr?- a)5 hours
- b)1 hour
- c)3 hours
- d)50 hours
Correct answer is option 'A'. Can you explain this answer?
How long would it take to travel 50 km traveling at a speed of 10 km/hr?
a)
5 hours
b)
1 hour
c)
3 hours
d)
50 hours
|
Bhaskar Chatterjee answered |
Given data:
Distance = 50 km
Speed = 10 km/hr
To find: Time taken to travel 50 km
Calculation:
We know that,
Speed = Distance/Time
⇒ Time = Distance/Speed
Substituting the given values, we get
Time = 50/10
Time = 5 hours
Therefore, the time taken to travel 50 km at a speed of 10 km/hr is 5 hours.
Answer: (a) 5 hours
Distance = 50 km
Speed = 10 km/hr
To find: Time taken to travel 50 km
Calculation:
We know that,
Speed = Distance/Time
⇒ Time = Distance/Speed
Substituting the given values, we get
Time = 50/10
Time = 5 hours
Therefore, the time taken to travel 50 km at a speed of 10 km/hr is 5 hours.
Answer: (a) 5 hours
Can you explain the answer of this question below:The ______ of a distance versus time graph is speed.
- A:
slope
- B:
y-intercept
- C:
origin
- D:
none of the answers
The answer is a.
The ______ of a distance versus time graph is speed.
slope
y-intercept
origin
none of the answers
|
|
Raghav Chatterjee answered |
The Relationship between Distance and Time
When an object moves, it covers a certain distance in a certain amount of time. The relationship between distance and time can be represented on a graph called a distance-time graph.
The Slope of a Distance-Time Graph
The slope of a distance-time graph represents the speed of the object. The slope is defined as the change in distance divided by the change in time. Mathematically, the slope can be written as:
Slope = Change in distance / Change in time
In other words, the slope of the graph gives us the rate at which the distance is changing with respect to time. This rate is the speed of the object.
Interpretation of the Slope
If the slope of the graph is steep, it means that the object is covering a large distance in a short amount of time. This indicates that the object is moving at a high speed.
If the slope of the graph is shallow, it means that the object is covering a small distance in a long amount of time. This indicates that the object is moving at a low speed.
Conclusion
Therefore, the correct answer to the given question is option 'A' - the slope of a distance versus time graph is speed. The slope of a distance-time graph gives us the speed of the object.
When an object moves, it covers a certain distance in a certain amount of time. The relationship between distance and time can be represented on a graph called a distance-time graph.
The Slope of a Distance-Time Graph
The slope of a distance-time graph represents the speed of the object. The slope is defined as the change in distance divided by the change in time. Mathematically, the slope can be written as:
Slope = Change in distance / Change in time
In other words, the slope of the graph gives us the rate at which the distance is changing with respect to time. This rate is the speed of the object.
Interpretation of the Slope
If the slope of the graph is steep, it means that the object is covering a large distance in a short amount of time. This indicates that the object is moving at a high speed.
If the slope of the graph is shallow, it means that the object is covering a small distance in a long amount of time. This indicates that the object is moving at a low speed.
Conclusion
Therefore, the correct answer to the given question is option 'A' - the slope of a distance versus time graph is speed. The slope of a distance-time graph gives us the speed of the object.
Distance covered by a body from velocity-time graph is- a)Equal to the slope of the graph.
- b)Area under the graph .
- c)Is denoted by a line parallel to the time axis at any point on the distance axis.
- d)Is denoted by a line parallel to the distance axis at any point on the time axis
Correct answer is option 'B'. Can you explain this answer?
Distance covered by a body from velocity-time graph is
a)
Equal to the slope of the graph.
b)
Area under the graph .
c)
Is denoted by a line parallel to the time axis at any point on the distance axis.
d)
Is denoted by a line parallel to the distance axis at any point on the time axis
|
|
Ravi Verma answered |
The area under the line in a velocity-time graph represents the distance travelled. To find the distance travelled in the graph above, you need to find the area of the light-blue triangle and the dark-blue rectangle. The width of the rectangle is 6 seconds and the height is 8 metres per second.
The speed-time graph for a particle moving at constant speed is a straight-line ________ to the time axis.- a)perpendicular
- b)parallel
- c)inclined
- d)aligned
Correct answer is option 'B'. Can you explain this answer?
The speed-time graph for a particle moving at constant speed is a straight-line ________ to the time axis.
a)
perpendicular
b)
parallel
c)
inclined
d)
aligned
|
|
Ananya Sharma answered |
The speed-time graph for a particle moving at constant speed is a straight-line parallel to the time axis.
If a person walked at 2 m/s for 12 s he/she would travel a distance of- a)24 m
- b)6 m
- c)4 m
- d)none of the answers
Correct answer is 'A'. Can you explain this answer?
If a person walked at 2 m/s for 12 s he/she would travel a distance of
a)
24 m
b)
6 m
c)
4 m
d)
none of the answers
|
Gayatri Kaur answered |
Distance = speed x time
= 2 m/s x 12 s
= 24 m
How far will a car travel in 25 min at 12 m/s?- a)24 km
- b)10 km
- c)18 km
- d)14 km
Correct answer is option 'C'. Can you explain this answer?
How far will a car travel in 25 min at 12 m/s?
a)
24 km
b)
10 km
c)
18 km
d)
14 km
|
|
Learning Education answered |
No. of seconds in 1 minute = 60 No. of seconds in 25 minutes = (60 x 25) = 1500 sec Speed = 12 m/s In 1500 sec distance travelled = (1500 x 12) = 18000 m or 18 km That is c) 18 km.
An object travels 20 m in 5 sec and then another 40 m in 5 sec. What is the average speed of the object?- a)6 m/s
- b)2 m/s
- c)12 m/s
- d)0 m/s
Correct answer is option 'A'. Can you explain this answer?
An object travels 20 m in 5 sec and then another 40 m in 5 sec. What is the average speed of the object?
a)
6 m/s
b)
2 m/s
c)
12 m/s
d)
0 m/s
|
Vikram Khanna answered |
Average speed= (Total Distance)/(Total time)
= (20 m + 40 m)/(5 sec + 5 sec)
=60 m/10 sec
=6m/s
- a)24 km
- b)10 km
- c)18 km
- d)14 km
Correct answer is 'C'. Can you explain this answer?
|
Shiksha Academy answered |
When the automobile moves at 12 m/s for 25 minutes, we must calculate the distance.
Hence the car will travel 18 km in 25 min at 12 m/s.
Hence the car will travel 18 km in 25 min at 12 m/s.
______________ describes how fast something is going, whereas, __________ describes how fast something is going in a certain direction.- a)rate, velocity
- b)rate, speed
- c)speed, velocity
- d)speed, acceleration
Correct answer is option 'C'. Can you explain this answer?
______________ describes how fast something is going, whereas, __________ describes how fast something is going in a certain direction.
a)
rate, velocity
b)
rate, speed
c)
speed, velocity
d)
speed, acceleration
|
|
Harshad Basu answered |
Explanation:
Example:
Suppose a car is moving with a speed of 30 km/h, but it is taking a U-turn and moving in the opposite direction. Then, the speed of the car remains the same, i.e., 30 km/h, but its velocity changes because the direction of motion has changed. The velocity of the car will be negative because it is moving in the opposite direction.
Therefore, option (c) is the correct answer as speed measures how fast an object is moving, whereas velocity measures how fast an object is moving in a particular direction.
- Speed: Speed is the measure of how fast an object is moving or the distance covered by an object in a given time interval. It is a scalar quantity and is measured in meters per second (m/s) or kilometers per hour (km/h).
- Velocity: Velocity is the measure of how fast an object is moving in a particular direction. It is a vector quantity and is measured in meters per second (m/s) or kilometers per hour (km/h).
Example:
Suppose a car is moving with a speed of 30 km/h, but it is taking a U-turn and moving in the opposite direction. Then, the speed of the car remains the same, i.e., 30 km/h, but its velocity changes because the direction of motion has changed. The velocity of the car will be negative because it is moving in the opposite direction.
Therefore, option (c) is the correct answer as speed measures how fast an object is moving, whereas velocity measures how fast an object is moving in a particular direction.
Speed of sound in water is 1500 m s-1, depth of water when reflected sound waves are detected after 0.40 s is
- a)700 m
- b)600 km
- c)300 m
- d)750 km
Correct answer is option 'C'. Can you explain this answer?
Speed of sound in water is 1500 m s-1, depth of water when reflected sound waves are detected after 0.40 s is
a)
700 m
b)
600 km
c)
300 m
d)
750 km
|
Shilpa nambiar answered |
To determine the depth of water using the speed of sound in water and the time it takes for the reflected sound waves to be detected, we can use the following steps:
- Speed of sound in water: 1500 m/s
- Time for the round trip: 0.40 s
The sound wave travels to the bottom of the water body and back to the surface, so the time taken for the sound to reach the bottom is half of the total time:
Time to reach the bottom=0.40/2=0.20 s
- Depth of the water can be calculated using the formula:
Distance=Speed×Time
Here, the distance to the bottom (which is the depth d) is:
d=1500 m/s×0.20 s=300 m
Thus, the depth of the water is 300 meters.
How far will a car travel in 25 min at 12 m/s?- a)24 km
- b)10 km
- c)18 km
- d)14 km
Correct answer is 'C'. Can you explain this answer?
How far will a car travel in 25 min at 12 m/s?
a)
24 km
b)
10 km
c)
18 km
d)
14 km
|
|
Ravi Verma answered |
Speed = Distance / TimeDistance = Speed x Time= 12 m/s x 25 min= 12 m/s x 25 x 60 sec= 18000 m=18 km
______ is a unit of speed:- a)m/s
- b)hr
- c)s
- d)kg
Correct answer is 'A'. Can you explain this answer?
______ is a unit of speed:
a)
m/s
b)
hr
c)
s
d)
kg
|
Amrita Sengupta answered |
Speed = distance /time unit of distance is m unit of time is S hence, unit of speed = m/s
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