you need to use hours to make it easy to convert to m/s. Change 15 minutes to hours
Note distance is in km so change the time to hours to get km/hour
1 hour = 60mins so 15 minutes will be 0.25 hours
10/0.25 = 40 km/ hour
To change that to m/second, change km to meters and hour to second
it will be (40x1000) meters /3600seconds
11.1111 m/s
Answer:
For a velocity versus time graph how do you know what the velocity is at a certain time?
Ans: By drawing a line parallel to the y axis (Velocity axis) and perpendicular to the co-ordinate of the Time on the x axis (Time Axis). The point on the slope of the graph where this line intersects, will be the desired velocity at the certain time.
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How do you know the acceleration at a certain time?

Hence,
By dividing the difference of the Final and Initial Velocity by the Time Taken, we could find the acceleration.
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How do you know the Displacement at a certain time?
Ans: As Displacement equals to the area enclosed by the slope of the Velocity-Time Graph, By finding the area under the slope till the perpendicular at the desired time, we find the Displacement.
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a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.