The correct answer is D) Ar
Answer:
a) 250 N
b) 50 N
c) 5000 J
d) 4
e) 3.33
Explanation:
Given that weight of piano (
) = 1000 N, distance moved by pulley (
) = 5 m and the rope used (
) =20 m
a) The effort applied (
) if it was an ideal machine is:

b) If the actual effort = 300 N
The force to overcome friction = actual effort -
= 300 - 250 = 50 N
c) Work output = 
d) ideal mechanical advantage (IMA) = 
e) Input force = 300 N, Therefore:
actual mechanical advantage =
/ input force = 1000 / 300 = 3.33
Answer:
BrF3 has 2 lone pairs (4 unshared electrons)
Explanation: