Answer:
<em>Reason:- We use cotton to make the wick of a spirit lamp because cotton has thread strands which act like fine capillaries and help in drawing up a steady supply of oil in the lamp for burning by capillary action</em>
Explanation:
- Demand of natural resources have influenced human settlement plans .
- Clean air,clean water and food are examples of natural resources
How demands became the obstacles ?
- The demands forces the human to go to different places in order to fulfill their requirements .
- So they have to shift their homes to different places .
Answer:
<u>E. Hydrogen</u>
Explanation:
It is important to note that since Hydrogen is categorized as the lightest known element in the universe today. <u>It is therefore the </u><u>only </u><u>gas molecules among the listed option that would be most likely be moving at a speed high enough to escape the earth's atmosphere.</u>
Because Hydrogen has just a single proton and a single electron this makes it easy to acquire enough energy to pull the earth's gravity.
Answer: a) 42 *10^-3 m= 42 mm; b) 10.40 *10^-6 s=10.40 μs
Explanation: In order to response this problem we have to consider the Newton law for the circular movement,
Fm=m*ac where Fm is the magnetci force and ac the centripetal acceleration which is equal to v^2*R ( the raduis of teh curcular trajectory)
Fm=e*v*B considering that v and B are perpendicular
then we have:
e*v*B=m*v^2/R so
R=m*v/(e*B)= 9.1*10^-31*1.44*10^7/(1.6*10^-19*1.95*10^-3)= 42 mm
Then to calculate the time to complete one revolution ( period)
we know that ω=v*R and T= 2π/ω
then we have:
ω=1.44*10^7*42*10^-3=604.8 *10^3 rad/s
T=2*π/604.8 *10^3 = 10.4 μs