What's+the+Mass?

What's The Mass?


 * Authors**: Ali S, Branden M, Younga K.


 * Abstact**: The goal of this lab is to determine the mass of an unknown object using concepts of momentum and impulse. Three methods were used to find the unknown mass. One dropping the unknown mass of sandbag onto the car moving at constant velocity, the other by creating a collision of two cars and lastly using a pulley and the impulse-momentum change equation. Finding the unknown mass in three different ways, we were able to estimate the mass to be about 800 grams.


 * Introduction**: We will be finding the unknown mass but also we will comprehend the conception of momentum and impulse. Since we mostly tried finding the final velocity, the concepts of momentum and impulse can be missed out which this lab is good to check the understanding. Using three different methods that are based on Impulse-momentum theorem as exerting the force on an object for a time interval, the law of conservation of momentum where total momentum of the system before equal to the after the collision, and the inelastic collision how only momentum is conserved are going to help to find the unknown mass and to have a better understanding.


 * Method****s+Results**:

[|lab_m1.bmp]
 * Method 1**: Inverse Clap

The set up for the first experiment was: 1 car (255g), sandbag F (unknown mass), motion detector.

We dropped the sand bag onto the car moving at constant velocity. The idea behind this method, was we would have the initial velocity of the car alone, and the final velocity of the car and the sandbag. The equation we used is as follows:

Mcar *Vinitial car = (Mcar + Msandbag)Vcar and sandbag

255(.702) = (255+x).3096 x=323.197 The mass of sandbag F that we calculated from our first trial was 323.197g.

.599(255) = (255+x).286 x=280.063 The mass of the sandbag that we calculated from the second trial was 280.063g.

We figured that there was a lot of human error involved in this method, because if the sandbag is dropped with even a little bit of horizontal velocity, the results will be off.



[|lab_m2.bmp]
 * Method 2**:

The second method we used in trying to discover the mass of the sandbag, involved creating a collision of two cars. One car was empty, the second car held our sandbag and began at rest. Using the motion detector, we measured the velocities of the cars. The equation we used is the same as the one stated above.

.637(255) = (255+255+x).109 x=984.57

.665(255) = (255+255+x).130 x=729.64

We found the mass of the sandbag to be 984.57g in our first trial, and 792.64g in our second trial using Method 2.



[|lab_m3.bmp]
 * Method 3**:

In Method 3, we had our sandbag resting in the car. The car was attached to the force prob, which was connected to Logger Pro. The car was connected by a string to a mass hanging off of the table. Releasing the mass which pulled the car, we were able to calculate mass of the cart (with the sandbag inside), and then by subtracting the mass of the cart we found the mass of the sandbag

Using the formula, Force * time = deltaV * m (we were solving for mass)

Trial 1: (we used a 100g mass to accelerate the car) t=1.18 sec F= .9094 N Change in V= .83 m/s

1.18(.9094) = .83x x=.859kg or 858.88g The mass of the sandbag was calculated to be 858.88g

Trial 2: (we used a 50g mass to accelerate the car) t= 1.8 sec F= .486 N Change in V= .53 m/s

1.8(.486) = .53x x=1.155kg or 1155.434g The mass of the sandbag was calculated to be 1155.434g



Method 2's trials resulted in similar answers for the mass of the sandbag. This method was also the most accurate out of the three because there was the least chance for human error or for the equipment to effect the results.


 * Conclusion**:

After conducting three different experiments, and completing multiple trials, the sandbag F can be estimated at about 800g. Although the first method gave us too little mass and the third method gave us too much mass, we were able to understand which method would work the best and that method gave us good results. Because there was a lot of room for error in the first and third methods we got masses that were a little off, but we believe that we achieved our goal of finding the mass by using concepts of momentum and impulse.