Magnitude of acceleration = (change in speed) / (time for the change) .
Change in speed = (ending speed) - (starting speed)
                            =       zero            - (43 m/s)
                            =          -43 m/s .
Magnitude of acceleration = (-43 m/sec) / (0.28 sec) 
                                          =  (-43 / 0.28)  (m/sec) / sec 
                                          =        153.57...  m/s²
                                          =        1.5...  x 10²  m/s²  .
        
                    
             
        
        
        
Dalton thought that atoms were indivisible particles, and Thomson's discovery of the electron proved the existence of subatomic particles. ... The positive and negative charges cancel producing a neutral atom. images.tutorvista.com. Later discoveries by Rutherford and others lead to additional revisions to atomic theory.
        
             
        
        
        
(a) The stress in the post is 1,568,000 N/m²
(b) The strain in the post is  7.61 x 10⁻⁶  
(c) The change in the post’s length when the load is applied is 1.9 x 10⁻⁵ m.
<h3>Area of the steel post</h3>
A = πd²/4
where;
 d is the diameter
A = π(0.25²)/4 = 0.05 m²
<h3>Stress on the steel post</h3>
σ = F/A
σ = mg/A
where;
- m is mass supported by the steel
- g is acceleration due to gravity
- A is the area of the steel post
σ = (8000 x 9.8)/(0.05)
σ = 1,568,000 N/m²
<h3>Strain of the post</h3>
E = stress / strain
where;
- E is Young's modulus of steel = 206 Gpa
strain = stress/E
strain = (1,568,000) / (206 x 10⁹)
strain = 7.61 x 10⁻⁶
<h3>Change in length of the steel post</h3>
strain = ΔL/L
where;
- ΔL is change in length
- L is original length
ΔL = 7.61 x 10⁻⁶ x 2.5
ΔL = 1.9 x 10⁻⁵ m
Learn more about Young's modulus of steel here: brainly.com/question/14772333
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Electrostatic forces are non-contact forces; they pull or push on objects without touching them