Answer:
a
Explanation:
because it has compact molecules
Hello,
To solve we need to know the formula for speed
The formula is D/T=S (Distance of time=speed)
Now all we have to do is plug in the numbers.
20/40= 1/2 or 0.5
SO the speed is 0.5 m/s
Have a great day!
We can use the law of conservation of energy to solve the problem.
The total mechanical energy of the system at any moment of the motion is:
![E=U+K = mgh + \frac{1}{2}mv^2](https://tex.z-dn.net/?f=E%3DU%2BK%20%3D%20mgh%20%2B%20%5Cfrac%7B1%7D%7B2%7Dmv%5E2)
where U is the potential energy and K the kinetic energy.
At the beginning of the motion, the ball starts from the ground so its altitude is h=0 and therefore its potential energy U is zero. So, the mechanical energy is just kinetic energy:
![E_i = K_i = \frac{1}{2}mv^2 = \frac{1}{2}(0.3 kg)(8.2 m/s)^2=10.09 J](https://tex.z-dn.net/?f=E_i%20%3D%20K_i%20%3D%20%20%5Cfrac%7B1%7D%7B2%7Dmv%5E2%20%3D%20%20%5Cfrac%7B1%7D%7B2%7D%280.3%20kg%29%288.2%20m%2Fs%29%5E2%3D10.09%20J%20%20)
When the ball reaches the maximum altitude of its flight, it starts to go down again, so its speed at that moment is zero: v=0. So, its kinetic energy at the top is zero. So the total mechanical energy is just potential energy:
![E_f = U_f](https://tex.z-dn.net/?f=E_f%20%3D%20U_f)
But the mechanical energy must be conserved, Ef=Ei, so we have
![U_f = K_i](https://tex.z-dn.net/?f=U_f%20%3D%20K_i)
and so, the potential energy at the top of the flight is