Using K.E=1/2MV^2
answer is 125joules
        
             
        
        
        
Answer:

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Explanation:
I just answer the second question 
 
        
             
        
        
        
Helium is lighter than air from the lungs.
Explanation:
A balloon filled with the air from lungs will sink to the ground but a balloon filled with Helium floats because helium is lighter than air. 
Air is a mixture of many gases. 
The air from the lungs is predominantly made up of carbon dioxide and water vapor. 
- Gram per mole of carbon dioxide is 44. Water vapor is 18. 
- Compared to helium which is 4, we see that the gas is lighter. 
- Since the gas is lighter, it will float in air. 
- The main component of air around us is nitrogen gas with a gram per mole of 28. 
- A balloon filled with more of air from the lungs weigh more than that will filled air around and even far more than helium gas. 
- This will cause a helium filled balloon to float. 
learn more: 
Density brainly.com/question/1698555
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Answer:
see below
Explanation:
a. 0.1886 x 12
=2.2632
This has 2 sig figures so the answer can only have 2 sig figures
2.3
b. 2.995 - 0.16685
=2.82815
The most accurate in the problem is to thousands place so our answer can only be accurate to the thousands place
2.828
c. 910 x 0.18945=172.3995
The  least number of significant figures is 3 so the answer can only have 3 significant figures
172
 
        
             
        
        
        
Answer:
  t = 1.58 s
Explanation:
given,
Speed of ranger, v = 56 km/h
                             v = 56 x 0.278 = 15.57 m/s
distance, d = 65 m
deceleration,a = 3 m/s²
reaction time = ?
using stopping distance formula


t is the reaction time

  t = 1.58 s
hence, the reaction time of the ranger is equal to 1.58 s.