Mech HW-56 Conservation of momentum in one dimension 2. a. A firecracker is at r
ID: 1448982 • Letter: M
Question
Mech HW-56 Conservation of momentum in one dimension 2. a. A firecracker is at rest on a frictionless horizontal table The firecracker explodes into two pieces of unequal mass that move in opposite directions on the table. Before Is the net force on the left piece always zero? Explain. After-tt i. After - ii. Is the net force on the system consisting of both pieces always zero? Explain. iii. Is the momentum of the left piece conserved? Explain. iv. Is the momentum of the system consisting of both pieces conserved? Explain b. A block slides down a frictionless incline. The incline is fixed in place on a table. Incline at rest Is the net force on the block always zero? Explain. i. ii. Is the net force on the incline always zero? Explain. ii. Is the net force on the block-incline system always zero? (Hint: Draw free-body diagrams for the block, incline, and system consisting of both objects.) Explain. iv. Is the momentum of the block conserved? Explain. v. Is the momentum of the incline conserved? Explain.Explanation / Answer
A)
i- No because it does have a mass and an acceleration.
ii- Yes, The net force on the system should equal zero, because after the explosion, they should have the same momentum. The left piece weighs less but is most traveling faster (according to the diagram arrows). The right piece weighs more but is traveling slower.
iii- Since there is constant kinetic energy, yes, the momentum will be conserved.
iv- Yes, the momentum of both pieces is conserved. The kinetic energy before the explosion is equal to the same kinetic energy after.
B)
i- As long as the block is sliding down the incline, there will be a force (gravity) exerted on the block, therefore the net force cannot equal zero.
ii- Yes, as long as the incline stays stationary, it's net force will equal zero.
iii- See answer of B-i for reference , [hint :gravitational force]
iv- If the block slides down the incline, then it is accelerating and changing kinetic energy, and would therefore not be conserved.
v- The momentum of the block-incline system is not conserved because there is no equal forces acting on the incline opposite to the net force that is acting on the block hence, the momentum of the entire system is not conserved.
C)
i- No. The net force is not equal to zero because there is now a x-component due to the downward force of weight.
ii- No. Because there is no force opposing the x component of the force that the block exerts on the incline.
iii- No. Because the system of block and incline is not isolated.The interaction between the block and the Earth [Gravitational Force] is not balanced with any other force.
iv- No, the momentum is not conserved beacuse there is a net force on the block.
v- No, the momentum is not conserved beacuse there is a net horizontal force on the incline.
vi- No, At first the momentum is zero. When the block is released the momentum of the block is down paralled to the incline, whereas themomentum of the incline is horizontal and to the left. These two vectors do not add up to zero. Therefore the momentum of the system is no longer zero. It has changed.
D)
i- No, beacuse they have gravitaional force and tension in the string try to adjust the block A.
ii- No, beacuse they have gravitaional force and tension in the strings try to adjust the blocks because they are of diffrent masses.
iii- No ,momentum is not conserved. beacuse thery will be accelation to the block A leading Kinetic Energy.
iv- No ,momentum is not conserved. beacuse thery will be accelation o the system leading diffrent Kinetic Energy.