# How do I find mass in this equation?

• Saucetray
In summary, the conversation discusses a problem about a child's toy that shoots ping pong balls using a spring. The problem asks for the height that the ball will reach when shot straight up. The attempt at a solution involves using the equations f=kx and f=mg, but the problem statement does not provide the mass of the ping pong ball. The correct mass can be found through a web search, and it is necessary to solve the problem. The conversation also brings up a discrepancy in the solution, which is clarified by considering the forces involved. Finally, it is mentioned that there may be an error in the problem statement itself.
Saucetray

## Homework Statement

A child’s toy that is made to shoot ping pong balls consists of a tube, a spring (k = 18 N/m) and a catch for the spring that can be released to shoot the balls. When a ball is loaded into the tube, it compresses the spring 9.5 cm. If you shoot a ping pong ball straight up out of this toy, how high will it go?

## Homework Equations

I know how to solve this... one thing gets in my way: the mass. The solution says it's .0027 but I hardly find that plausible.

## The Attempt at a Solution

I used f=kx and f = mg so mg=kx and m(9.81) = (18*.095m)
My answer is like .17 not .0027.. any ideas?

Last edited by a moderator:
The problem does not ask for you to find the mass of the ping pong ball, it asks for you to find the height achieved by said ball. The problem statement should have provided the mass of the ping pong ball. Without it you cannot solve the problem.

With missing data it is often possible to resort to a web search. If you google for the mass of a ping pong ball you'll find that the mass of a so-called official ping pong ball is 2.7 grams, or 0.0027 kg.

Saucetray said:
The solution says it's .0027
The solution says what is .0027? From gneill's post, I'm guessing it says that's the mass (in kg).
Saucetray said:
I used f=kx and f = mg so mg=kx
What circumstance corresponds to equating those two forces? Think about it.

Saucetray said:

## Homework Statement

When a ball is loaded into the tube, it compresses the spring 9.5 cm.

The problem text is wrong. It can not be the ball that compresses the spring by 9.5 cm. If the ball is compressed by the ball alone, the ball would never shot up.

## What is the definition of mass?

Mass is the amount of matter in an object. It is a measure of an object's resistance to acceleration. The more mass an object has, the more force is needed to accelerate it.

## How do I calculate mass?

Mass can be calculated by dividing the force acting on an object by its acceleration. The formula for mass is: mass = force / acceleration. It is important to use the correct units for force (usually newtons) and acceleration (usually meters per second squared).

## What is the unit of measurement for mass?

The SI unit of measurement for mass is kilograms (kg). However, other common units of measurement for mass include grams (g) and pounds (lbs).

## How do I find mass in a chemical equation?

In a chemical equation, the mass of a substance can be determined by multiplying its molar mass (grams per mole) by the coefficient in front of it. For example, in the equation 2H2 + O2 → 2H2O, the mass of water (H2O) is twice the molar mass of water.

## Can mass be created or destroyed?

No, according to the law of conservation of mass, mass cannot be created or destroyed. It can only be transformed from one form to another.

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