Answer:
 114.44 J
Explanation:
From Hook's Law,
F = ke................. Equation 1
Where F = Force required to stretch the spring, k = spring constant, e = extension.
make k the subject of the equation
k = F/e.............. Equation 2
Given: F = 10 lb = (10×4.45) N = 44.5 N, e = 4 in = (4×0.254) = 1.016 m.
Substitute into equation 2
k = 44.5/1.016
k = 43.799 N/m
Work done in stretching the 9 in beyond its natural length
W = 1/2ke²................. Equation 3
Given: e = 9 in = (9×0.254) = 2.286 m, k = 43.799 N/m
Substitute into equation 3
W = 1/2×43.799×2.286²
W = 114.44 J
 
        
                    
             
        
        
        
Answer:
Width of the slit will be equal to 1.47 mm
Explanation:
We have given wavelength of the light 
Distance D = 8 m 
Distance between first minimum dark fringe and the central maximum is 2 mm 
So 
We have to find the width of the slit
For the first order wavelength is equal to  , here a width of slit
, here a width of slit 
So 
So width of the slit will be equal to 1.47 mm
 
        
             
        
        
        
Answer:
V = 0.39 m/s
Explanation:
Given that,
Mass of hockey puck, m = 0.2 kg
Mass of goalie = 40 kg
Speed of hockey puck, v = 80 m/s
We need to find the speed with which the goalie slide on the slide. Let V be the speed. Using the conservation of momentum as follows :

So, the required speed is 0.39 m/s.
 
        
             
        
        
        
Infrared waves. The other 3 would hurt you because they are below the UV scale of 400 nanometers. Infrared is light that wouldn't harm you