1) A boy of mass 50kg runs up a staircase of 45 steps in 9 s. If the height of each step is 15cm.find his power. Take g=10m s-2. Page 156
Solutions : Weight of the boy.
Height of the staircase,
Time taken to climb, t=9 s
Power,P=Work done/time taken
= = 375 W Power is 375 W.
2) The unit of work is joule: Page 157
1 Joule = 1 Newton x 1 metre
3) What is echocardiography? Page 171
Answer:
Ultrasonic waves are made to reflect from various parts of the heart and form the images of
the heart. This technique is called echocardiography.
4) Electrons are ____________ charged,protons are ____________ charged and neutrons have ____
charges. Page 54
Answer: negatively ,positively ,no.
5) __________ virus is spread by the bite of infected dogs and others animals. Page 187
Answer: Rabies.
Solutions : Weight of the boy.
Height of the staircase,
Time taken to climb, t=9 s
Power,P=Work done/time taken
= = 375 W Power is 375 W.
2) The unit of work is joule: Page 157
1 Joule = 1 Newton x 1 metre
3) What is echocardiography? Page 171
Answer:
Ultrasonic waves are made to reflect from various parts of the heart and form the images of
the heart. This technique is called echocardiography.
4) Electrons are ____________ charged,protons are ____________ charged and neutrons have ____
charges. Page 54
Answer: negatively ,positively ,no.
5) __________ virus is spread by the bite of infected dogs and others animals. Page 187
Answer: Rabies.
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