A reconnaissance plane
flies 425 km away from its base at 212 km/h, then flies back to its base at 305
km/h. What is its average speed?
Answer: 250 km/h.
Total distance flown d = 425 + 425 = 850 km.
Total time flown t = 425/212 + 425/305 = 2.005 + 1.393 = 3.398 h
Average speed: v = d/t = 850 / 3.40 = 250 km/h.
A lever is used to lifta heavy load. when a 120 N force pushes one end of the lever down 75m , the load rises 0.25 m . Calculate the weight of the load ______N
If needed answer must be rounded into 3 significant figures
We have 120 N * 75 m = x N * 0.25 m
Then x = 120 * 75 / 0.25 = 36000 N is the weight or 3.60 x 10^4 N (to show 3 significant figures)
two automobiles each of mass 1250 kg are moving at the same speed , 25m/s when they collide and stick together. at what speed does the wreckage move if one car was driving north one south? ______m/s
Using conservation of momentum m_1*v_1 + m_2*v_2 = 1250*25 + 1250*(-25) = 0 = (m_1 + m_2)*u,
conclude that the speed after collision is 0 m/s.
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