A 3.2 kg ball that is moving straight upward has 17 Joules of kinetic energy. The total mechanical energy is 25 Joules. What is the ball’s height above the ground?

What is the speed of the ball?

h = 0.25 [m]

v = 3.26 [m/s]

Explanation:

In order to solve this problem, we must remember that mechanical energy is defined as the sum of kinetic energy plus potential energy.

E1 = Ek + Ep

where:

E1 = mechanical energy = 25 [J]

Ek = kinetic energy = 17 [J]

Ep = potential energy [J]

25 = 17 + Ep

Ep = 8 [J]

Now the potential energy is defined by the following equation:

Ep = m*g*h

where:

m = mass = 3.2 [kg]

g = gravity acceleration = 9.81 [m/s²]

h = elevation [m]

8 = 3.2*9.81*h

h = 0.25 [m]

The velocity can be calculated by means of kinetic energy.

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