Answer:
6logs
Explanation:f
First finding the volume of the logs
V= π/4d²l
= 0.098m³
So number of logs will be
Weight of 2 boys + weight of log = buoyancy force.
So
2( 400)+ N ( Mlog x g) = density of water x volume displaced x g
2(400) = N x 0.098x 1000x 9.8 x 0.9- 0.75* 1000
N= 5.5 which is approx 6logs
Answer:
17 * 10^5 J
Explanation:
From;
H= mcΘ
where;
m = mass of water = 5.0 Kg
c = heat capacity of water = 4 200 J/Kg °C
Θ = temperature rise = 100 °C - 20 °C = 80°C
Substituting values;
H = 5 * 4 200 * 80
H = 17 * 10^5 J
The equivalent resistance of n resistors connected in parallel is given by

(1)
In our problem, the resulting resistance of the 5 pieces connected in parallel is

, and since the 5 pieces are identical, their resistance R is identical, so we can rewrite (1) as

From which we find

.
So, each piece of wire has a resistance of

. Before the wire was cut, the five pieces were connected as they were in series. The equivalent resistance of a series of n resistors is given by

So if we apply it at our case, we have

therefore, the resistance of the original wire was

.
Answer:
3.2451N
Explanation:
Mass of the bullet (m) 
Speed of the bullet (V)
Rate of bullet (r) 
We can calculate with this information the average acceleration of bullets

The force is given by,

That is just because he is Superman.
Answer:
The external force leads to an increase on gravitational and spring potential energies.
Explanation:
The system consists of a mass, resort and Earth. According to the Principle of Energy Conservation there is a potential energy as a consequence of the interaction between Earth and the mass and spring potential energy because of the spring deformation and, besides, the existence of work due to an external force:



![F\cdot \Delta r = G\cdot m \cdot M \cdot \left(\frac{1}{r_{o}-\Delta r}-\frac{1}{r_{o}} \right)+\frac{1}{2}\cdot k \cdot [(x_{o}+\Delta r)^{2} -x_{o}^{2}]](https://tex.z-dn.net/?f=F%5Ccdot%20%5CDelta%20r%20%3D%20G%5Ccdot%20m%20%5Ccdot%20M%20%5Ccdot%20%5Cleft%28%5Cfrac%7B1%7D%7Br_%7Bo%7D-%5CDelta%20r%7D-%5Cfrac%7B1%7D%7Br_%7Bo%7D%7D%20%20%20%5Cright%29%2B%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20k%20%5Ccdot%20%5B%28x_%7Bo%7D%2B%5CDelta%20r%29%5E%7B2%7D%20-x_%7Bo%7D%5E%7B2%7D%5D)
The external force leads to an increase on gravitational and spring potential energies.