Please answer fast in 2 hours maximum
1) . A girl bends to touch her toes. Is the motion of her head an example of uniform motion or accelerated motion? Explain your answer
2) In the hare-tortoise race, the hare ran for 2 min at a speed of 7.5km/h, slept for 56 min and again ran for 2 min at a speed of 7.5km/h. Find the average speed of hare in the race.
3) A boy leaves his house at 9:30 am for his school. The school is 2 km away and classes start at 10:00 am. If he walks at a speed of 3km/h for the first km, at what speed should he walk the second km o reach just in time?
4)
A bus moves at a uniform speed v1 for some time and then with a uniform speed
v2 . The distance-time table is given below. Plot the corresponding Distance-time
graph and answer the following questions.
Time(min): 0 20 40 60 80 100 120
Distance(km):0 20 40 65 95 125 155
(a) Find the values of v1, v2
(b) When did the bus change its sped?
(c) What is the distance covered in first hour?
(d) What is the distance covered in second hour?
(e) What is the average speed for the complete journey?
5) An object dropped from a cliff falls with a constant acceleration of 10m/s2. Find its speed 2s after it was dropped
6) A ship moving with a constant acceleration of 36km/h
2in a fixed direction speeds up from 12km/h to 18 km/h. Find the distance traversed by the ship in this period.
1) Well it depends on how the body is moving w.r.t time. If the girl covers equal distances in equal interval of time while bending, then it is a uniform motion. But if it increases or decreases its speed while bending then its an accelerated motion.
2) total distance covered by the hare, s= 2(7.5*2/60) km = 0.5 km
total time taken, t = 60min = 1h
average speed, v = s/t = 0.5km/h
3) distance between the school and home, d = 2km
time taken to cover the first km, t1 = 1/3 h = 20 min
To reach class on time, the boy must cover the rest of 1 km in 10 min.
=> Speed of the boy should be, v = 1/10 km/min = 6km/h
4) According to the given data the bus changes its speed three times.
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(a) v1 = 1 km/min , v2 = 1.25km/min , v3 = 1.5km/min
(b) the bus changed its speed at t1 = 40 minutes and t2 = 60 minutes.
(c) Distance covered in first hour is 65 km.
(d) Distance covered in second hour is 90km.
(e) Total distance travelled, s = 155 km
Total time taken, t = 120 min = 2 h
=> average speed, v = s/t = 77.5 km/h
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