4. On a 100 km track a train travels the first 30 km at a uniform speed of 30 km/h.
How fast must the train travel the next 70 km so as to average 40 km/h for the entire trip?
5. (a) Identify the kind of motion in the following cases.
(i) A car moving with a constant speed turning around a curve.
(ii) An electron orbiting around nucleus.
(b) An artificial satellite is moving in a circular orbit of radius 36000 km.
Calculate its speed, if it takes 24 hours to revolve around the earth.
6. A car starts from rest and accelerates uniformly for 10 s to attain a velocity of 20 m/s.
If the mass of the car is 800 kg, find the force exerted by the car.
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Answer:
30km X 1=30
30km X 2=60
100 - 30=70 km left
Time taken for 70 km =
70-10 = 60+(10)
60+30km
1hr =30km
2hr =60km
3hr =90km
10km=1/3X60 =20min
It takes 3hr 2min for covering 100km
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