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Question
Figure shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?
Figure: Distance-time graph for the motion of two cars
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Solution
The speed is given by the relation
speed = `" distance travelled" / "time taken"`
This relation shows that the speed of a vehicle is high if it covers the maximum distance in a given time interval. To compare the distance, draw a line perpendicular to the time axis, as shown in the following distance-time graph
The graph clearly shows that for a given time t, vehicle A covers more distance than vehicle B. So, vehicle A is moving faster than vehicle B.
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RELATED QUESTIONS
Given figure shows the distance-time graph of three objects A, B and C. Study the graph and answer the following questions:
- Which of the three is travelling the fastest?
- Are all three ever at the same point on the road?
- How far has C travelled when B passes A?
- How far has B travelled by the time it passes C?
Show the shape of the distance-time graph for the motion in the following case:
A car moving with a constant speed.
Show the shape of the distance-time graph for the motion in the following case:
A car parked on a side road.
What can you say about the motion of a body whose distance-time graph is a straight line parallel to the time axis ?
Fill in the following blank with suitable word :
The slope of a speed-time graph of a moving body gives its………………………..
A spaceship is moving in space with a velocity of 60 kms−1. It fires its retro engines for 20 seconds and velocity is reduced to 55 kms−1. Calculate the distance travelled by a spaceship in 40 s, from the time of firing of the retro- rockets.
A body moves along a straight road with a speed of 20 m/s and has a uniform acceleration of 5 m/s2. What will be its speed after 2 s?
Two students were asked to plot a distance-time graph for the motion described by Table A and Table B.
| Table A |
||||||
| Distance moved (m) | 0 | 10 | 20 | 30 | 40 | 50 |
| Time (minutes) | 0 | 2 | 4 | 6 | 8 | 10 |
| Table B |
||||||
| Distance moved (m) | 0 | 5 | 10 | 15 | 20 | 25 |
| Time (minutes) | 0 | 1 | 2 | 3 | 4 | 5 |
The graph given in figure is true for
Assertion: The position-time graph of a uniform motion in one dimension of a body can have a negative slope
Reason: When the speed of the body decreases with time then, the position-time graph of the moving body has a negative slope.
What do you infer if
- Distance – time graph is a straight line.
- The velocity-time graph is curved.
- Displacement time is zigzag.
