Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
Initial velocity of spaceship = u = 60 kms−1
Final velocity of spaceship = v = 55 kms−1
It decelerates for 20 s
t = 20 s
v = u + at
55 = 60 + a (20)
20a = 55 – 60
20a = −5
a = `(-5)/20`
a = − 0.25
distance travelled in the first 20 sec. = s = u × t − `1/2` a × t2
s = 60 × 20 − `1/2` × 0.25 × 202
= 1200 − `1/2` × 0.25 × 400
= 1200 − `1/2` × 100
= 1200 − 50
= 1,150 km.
After 20 sec. the velocity of the spaceship is constant at 55 km/sec. Hence, the distance travelled is = 55 × 20 = 1,100 km
The total distance travelled in 40 sec. = 1,150 + 1,100 = 2,250 km
APPEARS IN
संबंधित प्रश्न
Show the shape of the distance-time graph for the motion in the following case:
A car moving with a constant speed.
Which of the following distance-time graphs shows a truck moving with speed which is not constant?
What does the slope of a distance-time graph indicate ?
Fill in the following blank with suitable word :
The slope of a distance-time graph indicates ………………….. of a moving body.
Four cars A, B, C and D are moving on a levelled, straight road. Their distance-time graphs are shown in the given figure. Which of the following is the correct statement regarding the motion of these cars?
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.
 |
 |
| (a) | (b) |
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?
Write down the type of motion of a body in each of the following distance time-graph.
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
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?
- Is the motion between 0 to 4 minutes uniform or non-uniform?
- What is his speed between 8 and 12 minutes of his journey?
