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प्रश्न
A cyclist is travelling at 15 m s-1. She applies brakes so that she does not collide with a wall 18 m away. What deceleration must she have ?
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उत्तर
We have to find the deceleration. We have the following information given,
Initial velocity, (u) = 15 m/s
Final velocity, (v) = 0 m/s
Distance travelled, (s) = 18 m
Let the acceleration be (a)
We can calculate acceleration by using the 3rd equation of motion,
`a = (v^2 - u^2)/(2s)`
Put the values in above equation to find the deceleration,
a = (0-225)/(36)
⇒ `a =-6.25 "m/s"^2`
Thus , the deceleration is 6.25 `"m/s"^2`
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संबंधित प्रश्न
What conclusion can you draw about the speed of a body from the following distance-time graph ?
Fill in the following blank with suitable word :
The slope of a distance-time graph indicates ………………….. of a moving body.
Fill in the following blank with suitable word :
The slope of a speed-time graph of a moving body gives its………………………..
A car is travelling at 20 m/s along a road. A child runs out into the road 50 m ahead and the car driver steps on the brake pedal. What must the car’s deceleration be if the car is to stop just before it reaches the child ?
Figure (a) shows the displacement-time graph for the motion of a body. Use it to calculate the velocity of the body at t = 1 s, 2 s and 3 s, and then draw the velocity-time graph in Figure (b) for it.
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| (a) | (b) |
Two friends leave Delhi for Chandigarh in their cars. A starts at 5 am and moves with a constant speed of 30 km/h, whereas B starts at 6 am and moves with a constant speed of 40 kmh-1. Plot the distance-time graph for their motion and find at what time the two friends will meet and at what distance from Delhi.
If we denote speed by S, distance by D and time by T, the relationship between these quantities is ______.
Distance between Bholu’s and Golu’s house is 9 km. Bholu has to attend Golu’s birthday party at 7 o’clock. He started from his home at 6 o’clock on his bicycle and covered a distance of 6 km in 40 minutes. At that point, he met Chintu and he spoke to him for 5 minutes and reached Golu’s birthday party at 7 o’clock. With what speed did he cover the second part of the journey? Calculate his average speed for the entire journey.
Boojho goes to the football ground to play football. The distance-time graph of his journey from his home to the ground is given in the figure.
- What does the graph between points B and C indicate about the motion of Boojho?
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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.
