Question

A 0.547 kg pizza is thrown straight up in the air. At a height of 2.30 m above the surface of the earth it has a speed of 5.00 m/s. Calculate the total mechanical energy of the pizza crust.

Answer 1

Answer:

The total mechanical energy of the pizza crust is 19.2 J.

Explanation:

Mechanical energy is that which a body or a system obtains as a result of the speed of its movement or its specific position, and which is capable of producing mechanical work. Then:

Potential energy + kinetic energy = total mechanical energy

Kinetic energy is a form of energy. It is defined as the energy associated with bodies that are in motion and this energy depends on the mass and speed of the body.

Kinetic energy is defined as the amount of work necessary to accelerate a body of a certain mass and in a position of rest, until it reaches a certain speed.

Kinetic energy is represented by the following formula:

Ec = ½ *m*v²

Where Ec is kinetic energy, which is measured in Joules (J), m is mass measured in kilograms (kg), and v is velocity measured in meters over seconds (m / s).

In this case:

• m=0.547 kg
• v= 5 m/s

Replacing:

Ec = ½ *0.547 kg*(5 m/s)²

and solving you get:

Ec= 6.8375 J

On the other hand, potential energy is the energy that measures the ability of a system to perform work based on its position. In other words, this is the energy that a body has at a certain height above the ground.

Gravitational potential energy is the energy associated with the gravitational force. This will depend on the relative height of an object to some reference point, the mass, and the force of gravity. Then for an object with mass m, at height h, the expression applied to the gravitational energy of the object is:

Ep = m*g*h

Where Ep is the potential energy in joules (J), m is the mass in kilograms (kg) is h the height in meters (m) and g is the acceleration of fall in m / s² (approximately 9.81 m/s²)

In this case:

• m= 0.547 kg
• g= 9.81 m/s²
• h= 2.30 m

Replacing

Ep= 0.547 kg *9.81 m/s²* 2.30 m

and solving you get:

Ep= 12.342 J

So:

Total mechanical energy= 12.342 J + 6.8375 J

Total mechanical energy= 19.1795 J≅ 19.2 J

The total mechanical energy of the pizza crust is 19.2 J.