Figure shows the position-time graph of the motion of two boys

Answer

(a) A lives closer to school than B.

(b) A starts from school earlier than B.

(c) B walks faster than A.

(d) A and B reach home at the same time.

(e) B overtakes A once on the road.

Explanation:

(a) In the given x-t graph, it can be observed that distance OP < OQ. Hence, the distance of school from the A's home is less than that from B's home.

(b) In the given graph, it can be observed that for x = 0, t = 0 for A, whereas for x = 0, t has some finite value for B. Thus, A starts his journey from school earlier than B.

(c) In the given x-t graph, it can be observed that the slope of B is greater than that of A. Since the slope of the x-t graph gives the speed, a greater slope means that the speed of B is greater than the speed A.

(d) It is clear from the given graph that both A and B reach their respective homes at the same time.

(e) B moves later than A and his/her speed is greater than that of A. From the graph, it is clear that B overtakes A only once on the road.

Page 2

Answer

Speed of the woman = 5 km/h

Distance between her office and home = 2.5 km

Time Taken  =  Distance / Speed

= 2.5/5 =  0.5h = 30 min

It is given that she covers the same distance in the evening by an auto.

Now, speed of the auto = 25 km/h

Time Taken  =  Distance / Speed

= 2.5/25 =  1/10 h = 0.1 h = 6 min

The suitable x-t graph of the motion of the woman is shown in the given figure.

Aditya Raj Tiwari 2018-09-11 10:02:16

😊soo helpful

Page 3

Answer

Distance covered with 1 step = 1 m

Time taken = 1 s

Time taken to move first 5 m forward = 5 s

Time taken to move 3 m backward = 3 s

Net distance covered = 5 - 3 = 2 m

Net time taken to cover 2 m = 8 s

Drunkard covers 2 m in 8 s.

Drunkard covered 4 m in 16 s.

Drunkard covered 6 m in 24 s.

Drunkard covered 8 m in 32 s.

In the next 5 s, the drunkard will cover a distance of 5 m and a total distance of 13 m and falls into the pit.

Net time taken by the drunkard to cover 13 m = 32 + 5 = 37 s

The x-t graph of the drunkard's motion can be shown as:

King Fucker 2019-08-29 16:16:55

Amazing Explained

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Pratik Chavan 2019-08-29 16:20:13

Sahi hai

Pratik 2019-08-12 16:38:09

Nice

Page 5

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Question 6

Answer

Initial velocity of the car, u = 126 km/h = 35 m/s

Final velocity of the car, v = 0

Distance covered by the car before coming to rest, s = 200 m

Retardation produced in the car = a

From third equation of motion, a can be calculated as:

v2 - u2 = 2as

(0)2 - (35)2   =  2 x a x 200

a  = -  (35 x 35)   /   (2  x  200)

a =  -3.06 m/s2

From first equation of motion, time (t) taken by the car to stop can be obtained as:

v = u + at

t  = v - u / a 

= -35 /  -3.06  =  11.44 s

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