Hwk Problem: Mechanical Energy

• shawonna23
In summary, a 30 g bullet with a horizontal velocity of 516 m/s comes to a stop 19 cm within a solid wall. To find the change in its mechanical energy, conservation of energy can be used, with the initial kinetic energy of 1/2mv² and the final kinetic energy of 0. The magnitude of the average force from the wall stopping the bullet can be calculated by equating the change in kinetic energy to the traveled distance times the force, using the equation F = m*a.
shawonna23
A 30 g bullet, with a horizontal velocity of 516 m/s, stops 19 cm within a solid wall.
(a) What is the change in its mechanical energy?

(b) What is the magnitude of the average force from the wall stopping it?

For Part a, To find the change in mechanical energy, do I use the equation: ME=(1/2)mv^2 + mgh

For Part b, I can use this equation F=m*a

a. yes

b. yes

-------------

ME = (1/2)mv^2 + mgh
(1/2)(mass)(velocity squared) + (mass)(gravity)(height)

F = m*a
Force = mass * acceleration

use this to solve your problems

shawonna23 said:
A 30 g bullet, with a horizontal velocity of 516 m/s, stops 19 cm within a solid wall.
(a) What is the change in its mechanical energy?

(b) What is the magnitude of the average force from the wall stopping it?

For Part a, To find the change in mechanical energy, do I use the equation: ME=(1/2)mv^2 + mgh

For Part b, I can use this equation F=m*a

For a) You should use conservation of energy. i think you can assume that the height of the bullet remains the same, so there is no change in potential energy mgh. basically the clue is that you come in with velocity 516 m/s and you stop after 0.19 m.

The change in mechanical energy is calculated by realizing that the kinetic energy goes from 1/2mv² to 0

For b) assume all horizontal motions. You can calculate the force that makes the object stop from this equation : change in kinetic energy = traveled distance * Force

So you'd have 1/2*30*516² = 0.19 * F...Solve for F

marlon

Thanks guys, I got the answers and they were correct!

1. What is mechanical energy?

Mechanical energy is the energy possessed by an object due to its motion or position. It can be divided into two types: kinetic energy, which is the energy of motion, and potential energy, which is the energy stored in an object's position or shape.

2. How is mechanical energy calculated?

Mechanical energy can be calculated by adding the kinetic energy and potential energy of an object. The formula for mechanical energy is: E = KE + PE, where E is mechanical energy, KE is kinetic energy, and PE is potential energy. The units of mechanical energy are joules (J).

3. What factors affect an object's mechanical energy?

The two main factors that affect an object's mechanical energy are its mass and its velocity. An object with a greater mass or a higher velocity will have more mechanical energy than a lighter or slower object.

4. Is mechanical energy conserved in a closed system?

Yes, according to the law of conservation of energy, mechanical energy is conserved in a closed system. This means that the total amount of mechanical energy in a system remains constant, even if it is transferred between different forms of energy.

5. How is mechanical energy used in real-life applications?

Mechanical energy is used in a variety of real-life applications. Some examples include wind turbines, which convert the mechanical energy of wind into electricity, and roller coasters, which use mechanical energy to power their thrilling rides. Mechanical energy is also used in machines such as cars, bicycles, and elevators to perform work and make our daily tasks easier.

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