Momentum

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Conservation of Momentum

PART A: COLLISIONS

 

 

L1 = 2.5 cm                                        L2 = 2.5 cm

Repeat 5 times for each set of mass and start up choice. Construct 4 tables. For the first 2 tables glider m2 will initially be at rest. For the last 2 tables, both gliders have initial motion.

Caution, record velocity (thus momentum) to the right as positive and velocity (thus momentum) to the left as negative.

The second glider is initially at rest

Use the gliders with magnet
m1

(gr)

 m2

(gr)

 t1i

(s)

 t2i

(s)

 t1f

(s)

 t2f

(s)

 V1i = L1/t1i

(cm/s)

 V2i = L2/t2i

(cm/s)

 V1f = L1/t1f

(cm/s)

 V2f = L2/t2f

(cm/s)

 pi = m1 V1i + m2 V2i

(gr cm/s)

 pf = m1 V1f + m2 V2f

(gr cm/s)

 % Dif = |pi - pf|/ pi x100% 
510 515 0.060 0 0 0.068 42 0 0 37 21420 = 2.1x104 19055 = 1.9x104 9.5%
510 515   0       0          
510 515   0       0          
510 515   0       0          
510 515   0       0          
                         
m1 m2 t1i t2i t1f

(Use Memory)

 t2f V1i = L1/t1i V2i = L2/t2i V1f = L1/t1f V2f = L2/t2f pi = m1 V1i + m2 V2i pf = m1 V1f + m2 V2f % Dif = |pi - pf|/ pi x100% 
510 1015 0.046 0 0.227-0.046 = 0.181 0.093 54 0 -14 27 27540 = 2.8x104 20265 = 2.0x104 29%
510 1015   0       0          
510 1015   0       0          
510 1015   0       0          
510 1015   0       0          

 

Both gliders are initially in motion - OPTIONAL
m1 m2 t1i t2i t1f t2f V1i = L1/t1i V2i = L2/t2i V1f = L1/t1f V2f = L2/t2f pi = m1 V1i + m2 V2i pf = m1 V1f + m2 V2f % Dif = |pi - pf|/ pi x100% 
510 515                      
510 515                      
510 515                      
510 515                      
510 515                      
                         
m1 m2 t1i t2i t1f t2f V1i = L1/t1i V2i = L2/t2i V1f = L1/t1f V2f = L2/t2f pi = m1 V1i + m2 V2i pf = m1 V1f + m2 V2f % Dif = |pi - pf|/ pi x100% 
510 1015                      
510 1015                      
510 1015                      
510 1015                      
510 1015                      

Questions:

1. Was momentum conserved in each of your collisions? If not, try to explain any discrepancies.

2. If a glider collides with the end of the air track and rebounds, it will have nearly the same momentum it had before it collided, but in the opposite direction. Is momentum conserved in such a collision? Explain.

3. Suppose the air track was tilted during the experiment. Would momentum be conserved in the collision? Why or why not?

 

Conservation of Momentum

PART B: EXPLOSIONS

Note, since the negative value of the velocity is already considered in the equation below, record the absolute value of the velocities in the table.

pi  = pf => 0 = -m1 V1f + m2 V2f => m1 V1f = m2 V2f => m1/m2 = V2f / V1f

One glider has the plunger the other not

L1 = 2.5 cm                                        L2 = 2.5 cm
m1

(gr - no plunger)

 m2

(gr - with plunger)

 t1f

(s)

 t2f

(s)

 V1f = L1/t1f

(cm/s)

 V2f = L2/t2f

(cm/s)

 N1 = m1/m2 N2 = V2f /V1f % Dif = |N1- N2|/ N1 x100% 
510 500 0.049 0.051 51 49 1.02 0.96 6%
510 500              
510 500              
510 500              
510 500              
                 
510 1000 0.041 0.093 61 27 0.51 0.44 14%
510 1000              
510 1000              
510 1000              
510 1000              
                 
1010 500              
1010 500              
1010 500              
1010 500              
1010 500              
                 
1010 1000              
1010 1000              
1010 1000              
1010 1000              
1010 1000              
                 

Questions

1. Does the ratio of the velocities equal the ratio of the masses in each of the cases? In other words, is momentum conserved?

2. When carts of unequal masses push away from each other, which cart has more momentum? Is this expected theoretically?

3. When the carts of unequal masses push away from each other, which cart has more kinetic energy? Is this expected theoretically?