Correct Answers is A.
The machines gives us some mechanical advantage. This means the mechanical average makes the work output greater than the work input
Simple most example is a lever. The force applied is smaller and the output work is larger as compared to input.
Option B cannot be true, as there must be a force to get some work done.
Option C and D are inverse of what a machine is designed for. A small force can be exerted through a large distance to have a large force exerted through a small distance. Common Example of this principle is a screw opener.
Y = +1-3 = -2
X = -5+7 = +2
D = √2^2-2^2 = 2√1+1 = 2√2 km
The answer to this is D. Probability levels for finding statistical significance increase as statistical power decreases. The statement concerning statistical probability is not true as this is d.
I hope this helps!
Answer:
The critical stress required for the propagation of an initial crack 
= 21.84 M pa
Explanation:
Given data
Modulus of elasticity E = 225 × 
Specific surface energy for magnesium oxide is 
= 1 
Crack length (a) = 0.3 mm = 0.0003 m
Critical stress is given by 
= 
-------- (1)
⇒ 2 E = 2 × 225 × × 1 = 450 ×
⇒ 
a = 3.14 × 0.0003 = 0.000942
⇒ Put these values in equation 1 we get
⇒ = 
⇒ = 4.77 × 
⇒ = 2.184 × 
⇒ = 21.84 
⇒ = 21.84 M pa
This is the critical stress required for the propagation of an initial crack.
