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?

Respuesta :

Answer:

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.

[tex]E_{k} =\frac{1}{2} *m*v^{2}\\17 =\frac{1}{2} *3.2*v^{2} \\v= \sqrt{\frac{17*2}{3.2} }\\v = 3.26[m/s][/tex]

(a) The height of the ball will be h=0.25 m

(b) The speed of the ball will be [tex]V= 3.26\ \frac{m}{s}[/tex]

What will be the speed and the height of the ball?

It is given that

Mass of the ball m=-3.2kg

The kinetic energy of the ball = 17 j

The total mechanical energy of the ball = 25 J

(a) So the total mechanical energy is the sum of the kinetic energy of the ball and the potential energy of the ball.

[tex]E_T=E_{KE}+E_{PE}[/tex]

Now putting the values of the KE and the Total energy we get

[tex]25=17+E_{PE}[/tex]

[tex]E_{PE}=8 \ J[/tex]

Now the formula of the potential energy will be

[tex]E_{PE}=mgh[/tex]

[tex]8=3.2\times 9.81 \times h[/tex]

[tex]h= \dfrac{8}{3.2\times 9.81}[/tex]

[tex]h=0.25\ m[/tex]

(b) Now to find out the speed of the ball we have

[tex]E_K=17\ J[/tex]

[tex]E_K=\dfrac{1}{2} mv^2[/tex]

[tex]v=\sqrt{\dfrac{2E_{KE}}{m} }[/tex]

[tex]v=\sqrt{ \dfrac{2\times17}{3.2} }=3.25[/tex]

[tex]v=3.25 \ \dfrac{m}{s}[/tex]

So the calculated answers will be

(a) The height of the ball will be h=0.25 m

(b) The speed of the ball will be [tex]V= 3.26\ \frac{m}{s}[/tex]

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