Physics NAME ___________________________
Momentum Period ____________
Use the following site to answer the questions below.
http://www.glenbrook.k12.il.us/gbssci/phys/class/momentum/momtoc.html
Lesson 1: The Impulse-Momentum Change Theorem
1) Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers______________________________________________ A sports team which is on the move has the _________________. If an object is in motion (on the move) then it has __________________.
2) Momentum depends upon the variables _______and____________. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.
_______________= mass • velocity
In physics, the symbol for the quantity momentum is the lower case "____". Thus, the above equation can be rewritten as
p = ______________
where m = mass and v = velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity.
3) The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the ______________.
From the definition of momentum, it becomes obvious that an object has a ________ momentum if either its mass or its velocity is large. Both variables are of equal importance in determining the momentum of an object. Consider a Mack truck and a roller skate moving down the street at the same speed. The considerably greater mass of the Mack truck gives it a considerably ________________ momentum. Yet if the Mack truck were at rest, then the momentum of the least massive roller skate would be the ____________. The momentum of any object which is at rest is ____. Objects at rest _______ have momentum - they do not have any "___________________." Both variables - _______ and _________ - are important in comparing the momentum of two objects.
Check Your Understanding
Express your understanding of the concept and mathematics of momentum by answering the following questions. Click the button to view the answers.
5. Determine the momentum of a ...
a. 60-kg halfback moving eastward at 9 m/s.
b. 1000-kg car moving northward at 20 m/s.
c. 40-kg freshman moving southward at 2 m/s.
a.
b.
c.
6. A car possesses 20 000 units of momentum. What would be the car's new momentum if ...
a. its velocity were doubled.
b. its velocity were tripled.
c. its mass were doubled (by adding more passengers and a greater load)
d. both its velocity were doubled and its mass were doubled.
a.
b.
c.
d.
7. A halfback (m = 60 kg), a tight end (m = 90 kg), and a lineman (m = 120 kg) are running down the football field. Consider their ticker tape patterns below.
Compare the velocities of these three players. How many times greater is the velocity of the halfback and the velocity of the tight end than the velocity of the lineman?
8.Which player has the greatest momentum? Explain.
Lesson 2: The Law of Momentum Conservation
The Law of Action-Reaction
9. A collision is an ___________ between _______________ which have made contact (usually) with each other. As in any interaction, a collision results in a force being applied to the two colliding objects. Such collisions are governed by ____________________________________. In the second unit of The Physics Classroom, Newton's third law of motion was introduced and discussed. It was said that...
... in every interaction, there is a pair of forces acting on the two interacting objects. The size of the force on the first object _________ the size of the force on the second object. The direction of the force on the first object is ___________ to the direction of the force on the second object. Forces __________ come in pairs - equal and opposite action-reaction force pairs.
10. Newton's _________ law of motion is naturally applied to collisions between two objects. In a collision between two objects, both objects experience _________ which are __________ in magnitude and ______________ in direction. Such forces often cause one object to _________ up (gain momentum) and the other object to _________ down (lose momentum). According to Newton's third law, the forces on the two objects are equal in magnitude. While the forces are equal in magnitude and opposite in direction, the ________________ of the objects are not necessarily equal in magnitude. In accord with Newton's second law of motion, the acceleration of an object is dependent upon both _________ and _______. Thus, if the colliding objects have unequal mass, they will have ___________ accelerations as a result of the contact force which results during the collision.
11. Consider the interaction between a male and female figure skater in pair figure skating. A woman (m = 45 kg) is kneeling on the shoulders of a man (m = 70 kg); the pair is moving along the ice at 1.5 m/s. The man gracefully tosses the woman forward through the air and onto the ice. The woman receives the forward force and the man receives a backward force. The force on the man is ________ in magnitude and opposite in direction to the force on the woman. Yet the acceleration of the woman is ___________ than the acceleration of the man due to the smaller mass of the woman.
Check Your Understanding
Express your understanding of Newton's third law by answering the following questions. Click the button to check your answers.
1. While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?
2. For years, space travel was believed to be impossible because there was nothing which rockets could push off of in space in order to provide the propulsion necessary to accelerate. This inability of a rocket to provide propulsion in space is because ...
a. space is void of air so the rockets have nothing to push off of.
b. gravity is absent in space.
c. space is void of air and so there is no air resistance in space.
d. ... nonsense! Rockets do accelerate in space and have been able to do so for a long time.
3. Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases which expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ...
a. greater than the acceleration of the bullet.
b. smaller than the acceleration of the bullet.
c. the same size as the acceleration of the bullet.
4. Kent Swimm, who is taking Physics for the third year in a row (and not because he likes it), has rowed his boat within three feet of the dock. Kent decides to jump onto the dock and turn around and dock his boat. Explain to Kent why this docking strategy is not a good strategy.
5. A clown is on the ice rink with a large medicine ball. If the clown throws the ball forward, then he is set into backwards motion with the same momentum as the ball's forward momentum. What would happen to the clown if he goes through the motion of throwing the ball without actually letting go of it? Explain.
6. Chubby, Tubby and Flubby are astronauts on a spaceship. They each have the same mass and the same strength. Chubby and Tubby decide to play catch with Flubby, intending to throw her back and forth between them. Chubby throws Flubby to Tubby and the game begins. Describe the motion of Chubby, Tubby and Flubby as the game continues. If we assume that each throw involves the same amount of push, then how many throws will the game last?
7. Go to the animation box at the bottom of the page and answer the following question. How fast do the two of you move after the collision?
Lesson 2: The Law of Momentum Conservation
Momentum Conservation Principle
12. One of the most powerful laws in physics is the law of momentum conservation. The law of momentum conservation can be stated as follows.
13. The above statement tells us that the _________ ____________________ of a collection of objects (a system) is conserved - that is, the total amount of momentum is a ____________ or __________________ value.
14. The above equation is one statement of the law of __________________ conservation. In a collision, the momentum change of object 1 is ___________ to and ________________ of the momentum change of object 2. That is, the momentum lost by object 1 is equal to the momentum ___________ by object 2. In most collisions between two objects, one object slows down and loses momentum while the other object speeds up and gains momentum. If object 1 loses 75 units of momentum, then object 2 gains 75 units of momentum. Yet, the total momentum of the two objects (object 1 plus object 2) is the _________ before the collision as it is after the collision. The total momentum of the system (the collection of two objects) is ______________.
15. Go to the ANIMATION BOX. Answer the following questions.
a. What was the initial momentum of the cart?
b. What was the initial momentum of the dropped brick?
c. What was the final momentum of the cart?
d. What was the final momentum of the dropped brick?
e. What was the total initial momentum of the system?
f. What was the total final momentum of the system?
Check Your Understanding
Express your understanding of the concept and mathematics of momentum by answering the following questions. Click on the button to view the answers.
1. When fighting fires, a firefighter must use great caution to hold a hose which emits large amounts of water at high speeds. Why would such a task be difficult?
2. A large truck and a Volkswagen have a head-on collision.
a. Which vehicle experiences the greatest force of impact?
b. Which vehicle experiences the greatest impulse?
c. Which vehicle experiences the greatest momentum change?
d. Which vehicle experiences the greatest acceleration?
3. Miles Tugo and Ben Travlun are riding in a bus at highway speed on a nice summer day when an unlucky bug splatters onto the windshield. Miles and Ben begin discussing the physics of the situation. Miles suggests that the momentum change of the bug is much greater than that of the bus. After all, argues Miles, there was no noticeable change in the speed of the bus compared to the obvious change in the speed of the bug. Ben disagrees entirely, arguing that that both bug and bus encounter the same force, momentum change, and impulse. Who do you agree with? Support your answer.
4. If a ball is projected upward from the ground with ten units of momentum, what is the momentum of recoil of the Earth? ____________ Do we feel this? Explain.
5. If a 5-kg bowling ball is projected upward with a velocity of 2.0 m/s, then what is the recoil velocity of the Earth (mass = 6.0 x 1024 kg).
6. A 120 kg lineman moving west at 2 m/s tackles an 80 kg football fullback moving east at 8 m/s. After the collision, both players move east at 2 m/s. Draw a vector diagram in which the before- and after-collision momenta of each player is represented by a momentum vector. Label the magnitude of each momentum vector.