Q Name the cells having branches structure. Ans Nerve Cell. Q Why cells could not be observed before seventeenth century? Ans Cells could not be observed before seventeenth century because till that time microscope was not invented. Q Why plant cell have cell wall? Ans Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture, etc. They are exposed to these variations because they cannot move. That's why they have cell wall. Q Which organism has the smallest cell? Ans Mycoplasmas, a bacteria has the smallest cell of the size of 0.1 micron i.e. ten thousandth part of a mill metre. ' Q Which is the largest cell visible by unaided eye? Ans Ostrich egg has the largest visible cell by unaided eye. Q Name the four elements, which fonn major part of protoplasm. Ans These are carbon, hydrogen, oxygen and nitrogen. Q Give two examples of prokaryotes. Ans Bacteria and blue green algae. Q Name the largest organ
1) A bullet blasts from the barrel of a gun upward in the vertical direction with an initial speed of 700 m/s. Find the maximum altitude reached by this bullet and the time needed to reach it.
ReplyDeleteInitial speed u = 700 m/s Final speed v =0m/s (at the maximum altitude) , a = -10m/s2
t = ( v-u)/0 =( 0 – 700)/-10 = 70m/s
v2 = u2 + 2as
v2 - u2)/ 2a =s
0 – (700)2 /2x-10
= - 490000/-20 = 24500m
2) A mouse is dropped from an eagle's claws starting at an altitude of 150 meters. What distance does it fall in the third second after it is dropped?
S = ut + ½ at2
0x3 + ½ x 10 x3x3
= 45m
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