The answer is the first one
Answer:
<em>a. True</em>
<em></em>
Explanation:
I'll assume the question is about magnetic latches and locks.
Magnetic door locks use an electromagnetic force to stop doors from opening, so they are ideal for security. There are two main types of electric locking devices. Locking devices can either be a fail-secure locking device that remains locked when power is lost, or a fail-safe locking device that is unlocked when de-energized. An electromagnetic lock creates a magnetic field when energized or powered up, this causes an electromagnet and armature plate to become attracted to each other strongly enough to keep a door from opening.
B. 1520 is the difference between their weights.
<em>Answer: </em>
tim e (t) = 20 min.
= 20 × 60 = 1200 s ,
Work ( W) = 4560000 J
= 4560 KJ ,
Determine:
Power output (P) = Work ÷ time
= 4560 ÷ 1200
<em> P = 3.8 KW</em>
cos(A) = (b2 + c2 − a2) / 2bc = (16+6.5^2-3.5^2)/(2*4*6.5) = 0.88461538 so A = cos−1 (0.88461538) = 27.79 Deg
cos(B) = (c2 + a2 − b2)/2ca = (3.5^2+6.5^2-16)/(2*3.5*6.5) = 0.84615385 so B = cos−1 (0.84615385) = 32.2 Deg
