Answer:B
Explanation:
Given
For motor A
Characteristic life(r)=4100 hr
MTTF=4650 hrs
shape factor(B )=0.8
For motor B
Characteristic life(r)=336 hr
MTTF=300 hr
Shape Factor (B)=3
Reliability for 100 hours



For B


B is better for 100 hours
(b)For 750 hours


So here B is more Reliable.
Answer:
It has poor tensile strength despite having high compressive strength
Explanation:
Concrete exhibits high compressive strength when used. However, it has very low compressive strength. This is the reason why concrete is normally combined with steel to make a composite building material called reinforced concrete. The steel reinforces concrete hence increasing the tensile strength in RC buildings. The end composite is durable and fireproof. Generally, the main reason why concrete is not use on its own is due to its poor tensile strength.
Given:
Temperature of water,
=
=273 +(-6) =267 K
Temperature surrounding refrigerator,
=
=273 + 21 =294 K
Specific heat given for water,
= 4.19 KJ/kg/K
Specific heat given for ice,
= 2.1 KJ/kg/K
Latent heat of fusion,
= 335KJ/kg
Solution:
Coefficient of Performance (COP) for refrigerator is given by:
Max
= 
=
= 9.89
Coefficient of Performance (COP) for heat pump is given by:
Max
= 
= 10.89
Answer:
Maximum height=7.3535 m
Explanation:
Solution of the problem is given in the attachments.