Physics Q's help ASAP

[ahmed]

Just don't understand these Electricity Q's:

Q1
    
Three children, each of weight 356 N, make a log raft by lashing together logs of diameter 0.30 m and length 1.80 m. How many logs will be needed to keep them afloat in fresh water? Take the density of the logs to be 800 kg/m3.

Q2

In Fig. 21-26a(attached below), particles 1 and 2 have charge 20.0 micro Coulombs each and are held at separation distance d=1.5m. (a) What is the magnitude of the electrostatic force on particle 1 due to particle 2? (b) In Fig. 21-26b, particle 3 of charge 20.0 uC (u=micro) is positioned so as to complete an equilateral triangle. What is the magnitude of the net electrostatic force on particle 1 due to particles 2 and 3?

Q3

A current of 0.300 A(C/s) through your chest can send your heart into fibrillation, ruining the normal rhythm of heartbeat and disrupting the flow of blood (and thus oxygen) to your brain. If that current persists for 2.00 min, how many conduction electrons pass through your chest?

Q4
    
In Fig. 22-36(attached below) , the three particles are fixed in place and have charges q1=q2=+e and q3=+2e. Distance a=6 microns. What are the (a) magnitude and (b) direction of the net electric field at point P due to the three particles?

Q5

A uniform electric field exists in a region between two oppositely charged plates. An electron is released from rest at the surface of the negatively charged plate and strikes the surface of the opposite plate, 2.0 cm away, in a time 1.5 x 10^(-8) s. (a) What is the speed of the electron as it strikes the second plate? (b) What is the magnitude of the electric field E?

Thanks for the help in advance.

[pHysiX]

Haha. Qu1 is not electricity 

QU3:

0.3A = 0.3C/s

so in 2 minutes, there will be 36C.

One electron = 1.6x10^-19C

So 36C must be 2.25x10^20 electrons

[ahmed]

I need help with the rest of the Q's excluding 1 and 3. I understood Q1 and 3, but need to understand the rest.

Thanks for the help in advance.