Answer:
The potential energy increases and the kinetic energy decreases
 
        
             
        
        
        
Answer:
m = 0.51[kg]
Explanation:
Potential energy is defined as the product of mass by gravity by height.

where:
Epot = potential energy = 15 [J]
m = mass [kg]
g = gravity acceleration = 9.8 [m/s²]
h = elevation = 3 [m]
Now replacing:
![E_{pot}=m*g*h\\15=m*9.8*3\\m = 0.51[kg]](https://tex.z-dn.net/?f=E_%7Bpot%7D%3Dm%2Ag%2Ah%5C%5C15%3Dm%2A9.8%2A3%5C%5Cm%20%3D%200.51%5Bkg%5D)
 
        
             
        
        
        
the isotope they use is carbon-14
 
        
             
        
        
        
Answer:
  v₀ = 13.24 m / s
Explanation:
Let's use Newton's second law to find the average acceleration during the crash
        F = m a
.       a = F / m
        a = 8000/73
        a = 109.59 m / s²
Now we can use the kinematic equations to find the initial velocity, since when the velocity stops it is zero (v = 0)
        v² = v₀² - 2 a x
        v₀² = 2 a x
        v₀ = √  2 a x
        v₀ = √ (2 109.59 0.80)
        v₀ = 13.24 m / s