# Projectile Motion : Work and Energy

• ReCryptic
If you really want the thread deleted, use the Report button (red triangle, bottom left of every post) and ask for the thread to be deleted.What is the problem?In summary, the conversation was about a projectile-spring launcher and finding the work done on a ball by the spring. The given information included the displacement of the spring, mass of the ball, initial height and velocity, and the calculation of kinetic energy. The final step was to determine the spring constant, which was found to be 160 N/m. The person then asked for clarification on the placement of a decimal point, but later figured it out and requested for the post to be deleted, which may not be possible on
ReCryptic
Homework Statement
Estimate the amount of work done on the ball by the spring.
Relevant Equations
Work for spring = -1/2kxf^2 + 1/2kxi^2
Kinetic Energy = 1/2mv^2
Potential Spring Energy = 1/2kx^2
The problem is based on a projectile-spring launcher. A ball is loaded into a tube that pushes back a spring and is then launched. The ball was launched straight horizontally not at an angle.

I'm trying to find the work done on the ball by the spring.

The info I have:

Displacement of spring = .05m
Mass of ball = .010kg
Initial height = 0m.
Initial velocity of ball after launch = 2 m/s.

KE = 1/2mv^2
= 1/2 * .01kg * 2m/s^2 = .2J

The spring energy is converted to Kinetic energy after launch so KE = Uspring.

KE = Uspring
.2J = 1/2kx^2
.2J = 1/2k*(.05m)^2
80 = 1/2k
k = 160 N/m.

Is my work so far correct?

ReCryptic said:
1/2 * .01kg * 2m/s^2 = .2J
Is the decimal point misplaced?

Which one?

I figured it out can you delete the post please?

ReCryptic said:
I figured it out can you delete the post please?
On PF, once a post has received help, the thread is never* deleted.

* almost never

## What is projectile motion?

Projectile motion is the motion of an object through the air or in a vacuum, under the influence of gravity. It is characterized by the object's initial velocity and angle of launch.

## How does projectile motion relate to work and energy?

Projectile motion involves both work and energy. Work is done on the object as it moves through the air, and energy is constantly being transferred between kinetic energy (motion) and potential energy (height).

## What affects the trajectory of a projectile?

The trajectory of a projectile is affected by the object's initial velocity, angle of launch, and the force of gravity. Air resistance and other external factors may also play a role.

## How is the work done on a projectile calculated?

The work done on a projectile can be calculated by multiplying the force acting on the object by the distance it travels in the direction of the force. In projectile motion, this can be represented by the change in potential energy as the object moves through the air.

## What are some real-world examples of projectile motion?

Some real-world examples of projectile motion include throwing a ball, shooting a basketball, and launching a rocket into space. Projectile motion is also seen in sports such as football, baseball, and golf.

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