Answer:
All trenches must have access/egress - A.
Answer:
-730KJ
Explanation:
According to the first law of thermodynamics;
Let the total energy of the system be ∆E
Let heat be q and let work the w
Since the energy decreases ∆E is negative
Since work is done on the system w= positive
So;
- 250 = 480 + q
q = -250 - 480
q=-730KJ
Answer:
The paintball ball launcher
Explanation:
The average speed of a paintball ball(vo) is approximately 90m/sec
and if the average speed of a ball pitcher in baseball (v1) is 150km/h
, which is equivalent to (150km/h*1000m/km*h/3600sec) = 41.66m/sec therefore the flight time of each mobile must be found to determine which one falls to the ground first
finally you can see that the shortest flight time is from the paintball ball launcher, therefore it will fall to the ground first
Note: Since the launch conditions must be the same for both, except the speed, it is placed 15º as an average value, but it can be any angle as long as it is the same for both
Answer:
- Direct current is a current in which electrons flow in one direction only
- Alternating current is a current in which the direction of the electron flow reverses periodically - so, half a cycle forward, half a cycle backward
There are several advantages of using alternating currents for the transmission of electricity across a country, over large distances. The main advantages are:
- The voltage of alternating currents can be easily increased/decreased by using transformers. For instance, a transformer is used at the beginning of the transmission line to increase the voltage (electricity is transmitted at high voltage in order to reduce dissipated power), and then another transformer is used before the electricity enters the houses, in order to decrease the voltage. Transformers only work with alternating currents.
- It is easy to interrupt the flow of an alternating current, because its value naturally becomes zero every half a cycle, so this is useful in case the current must be interrupted.