 # Finding the mass of an unknown object using its inertia

In this instance, it is assumed that "inertial force" refers to the amount of force it would take to move a certain object or stop it from moving entirely.

On the earth's surface, the mass of an object is roughly equal to its weight in kilograms, so you can find the mass by simply weighing the object on a scale. Find the object's rate of acceleration. If you are trying to gauge the inertial force of a moving object a car, for example and its rate of acceleration is unknown to you, you will need a speedometer to find its rate of acceleration. You can do this by measuring the speed of the object at one point in time and then measuring it again a few seconds later. This is because acceleration is the measure of how fast an object is increasing its speed over time.

## Mass, Weight and Gravity

Sciencing Video Vault Mark the times at which you measured the object's speed. Subtract the first speed from the second speed.

1. There are two masses, one sitting on a table, attached to the second mass which is hanging down over a pulley.
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3. In this instance, it is assumed that "inertial force" refers to the amount of force it would take to move a certain object or stop it from moving entirely.

Then divide the result by the amount of time between the two measures. If you measure a car rolling at 40 mph at 1: This means that, if the car maintained its current rate of acceleration, its speed would increase by 59 miles every hour.

Keep in mind that this equation assumes that the car is accelerating at a constant rate and doesn't take outside variables, such as gravity or friction, into account. Multiply the object's mass by its acceleration.

This will give you its inertial force. In the case of the car, we will assume its mass is about 1,000 kilograms.

## How to Calculate Inertial Force of Mass

If it maintains its current rate of acceleration, it would require approximately 59,000 kg about 65 tons of counter-force to stop it instantaneously. The amount of inertial force required to stop a moving object will be exactly equal to the amount of inertial force that set it into motion in the first place.

This is why a small object that is moving very quickly such as a bullet and a large object that is moving very slowly such as a boulder are both equally destructive and difficult to stop without the proper amount of counter-force. If the object is not moving, the amount of inertial force required to move it is generally equal to the mass of the object. The standard rate of miles per hour was substituted to make the example more understandable. 