Momentum practice problems (answers included)
Review the notes on the blog (2 posts ago) and try these questions and problems (similar to what we did in class today, Monday 4/2).
1. Give an example of 2 different conservation laws.
2. What is the mathematical definition of momentum?
3. What is the conservation of momentum, and when do we think about it (under what specific circumstances)?
4. A 300-g cart moving at 40 cm/s hits another 300-g at rest. Friction is very low. What do you expect will happen exactly? Give numbers if possible.
5. A 60-kg figure skater skating at 8 m/s collides directly with a 40-kg skater initially at rest. Friction is very low and the two become intertwined on the ice. Calculate the speed of the two of them together after the collision. (Hint: First find the momentum of the 60-kg skater, and then use conservation of momentum to solve for the final speed of the two together. This is like the velcro cart collisions.)
6. (Challenge problem) A 2-kg ball is traveling at 4 m/s and it hits another ball (initially at rest). The 2-kg ball continues to move forward at 3 m/s and the second ball moves forward in the same direction as the original ball at 2 m/s. How massive is the second ball? (Hint: Find the original momentum pre-collision, and then set that equal to the total momentums of the two balls after the collision, keeping the second ball's mass as m.)
Answers
1-3 See notes
4. Second car moves forward at approximately 40 cm/s. First car stops.
5. 4.8 m/s
6. second ball mass is 1 kg
1. Give an example of 2 different conservation laws.
2. What is the mathematical definition of momentum?
3. What is the conservation of momentum, and when do we think about it (under what specific circumstances)?
4. A 300-g cart moving at 40 cm/s hits another 300-g at rest. Friction is very low. What do you expect will happen exactly? Give numbers if possible.
5. A 60-kg figure skater skating at 8 m/s collides directly with a 40-kg skater initially at rest. Friction is very low and the two become intertwined on the ice. Calculate the speed of the two of them together after the collision. (Hint: First find the momentum of the 60-kg skater, and then use conservation of momentum to solve for the final speed of the two together. This is like the velcro cart collisions.)
6. (Challenge problem) A 2-kg ball is traveling at 4 m/s and it hits another ball (initially at rest). The 2-kg ball continues to move forward at 3 m/s and the second ball moves forward in the same direction as the original ball at 2 m/s. How massive is the second ball? (Hint: Find the original momentum pre-collision, and then set that equal to the total momentums of the two balls after the collision, keeping the second ball's mass as m.)
Answers
1-3 See notes
4. Second car moves forward at approximately 40 cm/s. First car stops.
5. 4.8 m/s
6. second ball mass is 1 kg
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