Momentum and impulse and other kinetic questions

[JWHooper]

1. What is the basic SI unites for momentum and impulse?
2. Know whether impulse and momentum are vector or scalar quantities.
3. What does it mean for a system to be isolated?
4. Differentiate between external and internal forces.
5. Differentiate between elastic and inelastic collisions.
6. Know which type of inelastic collision produces the greatest loss of kinetic energy.
7. Know what happens to kinetic energy in an inelastic collision.
8. Understand and apply Newton's Third Law of Motion.

I am having a little difficulty understanding these stuff. Can anyone help a little bit?


Thanks,

J.

 

[Astronuc]

We request that students show some work and effort when requesting assistance.

SI units are pretty basic, based on meter (m), kilogram (kg) and second (s).

What is the property of momentum? What is impulse?

Browse here and look for some of the terms mentioned -
http://hyperphysics.phy-astr.gsu.edu/hbase/impulse.html


Please try to answer each question on one's own.

 

[physixguru]

This is being given just to help you understand the ques better and some help in solving the above mentioned problems...with these hints you are expected to show some work..

1.momentum=m*v ; impulse=force*time

2.i=force*time; force=vector>>vector *scalar=??

p=mass*velcity ; velocity=vector, mass=scalar>>vector*scalar=?

3.related to force concepts.

4.Internal force: Forces which hold an object together when external forces or other loads are applied. Internal forces are sometimes called resisting forces since they resist the effects of external forces.
External force:A surface force or body force acting on an object. External forces are sometimes called applied forces.

5.Collision of cars on a road--inelastic collision.
Elastic collision:When two steel balls collide, they squash a little near the surface of contact, but then they spring back.

6.Collision of mud with a fixed wall is purely inelastic.

7.Use the above concept.
8.A force is a push or a pull upon an object which results from its interaction with another object. Forces result from interactions! Some forces result from contact interactions (normal, frictional, tensional, and applied forces are examples of contact forces) and other forces are the result of action-at-a-distance interactions (gravitational, electrical, and magnetic forces). According to Newton, whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body. There are two forces resulting from this interaction - a force on the chair and a force on your body. These two forces are called action and reaction forces and are the subject of Newton's third law of motion. Formally stated, Newton's third law is:

For every action, there is an equal and opposite reaction.

The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs.

A variety of action-reaction force pairs are evident in nature. Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. But a push on the water will only serve to accelerate the water. Since forces result from mutual interactions, the water must also be pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction force. Action-reaction force pairs make it possible for fish to swim.

Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. Since forces result from mutual interactions, the air must also be pushing the bird upwards. The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for birds to fly.

Consider the motion of a car on the way to school. A car is equipped with wheels which spin backwards. As the wheels spin backwards, they grip the road and push the road backwards. Since forces result from mutual interactions, the road must also be pushing the wheels forward. The size of the force on the road equals the size of the force on the wheels (or car); the direction of the force on the road (backwards) is opposite the direction of the force on the wheels (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for cars to move along a roadway surface.

check your understanding.::

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 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.

Post your answer.

 

[JWHooper]

Well, I remembered my physics teacher was talking about the space relating with the rocket motion. I believe that the answer is b. ... gravity is absent in space. Although the planets have gravity, the empty space universe has zero gravity.

 

[_Mayday_]

JWHooper, I would advise loking up the definition of a scalar and vector quantities and then doing the same for momentum and impulse, that should clear that question up. Are you working from a textbook?

 

[JWHooper]

Yes, I'm working from a textbook.

Scalar means just the momentum, and vector means both momentum and direction.
Momentum: p=mv
Impulse: F(delta)t = m(delta)v

 

[JWHooper]

Yes, I'm working from a textbook.

Scalar means just the magnitude, and vector means both magnitude and direction.
Momentum: p=mv
Impulse: F(delta)t = m(delta)v

 

[JWHooper]

It's supposed to be magnitude not momentum, sorry about that.

 

[physixguru]

Well, I remembered my physics teacher was talking about the space relating with the rocket motion. I believe that the answer is b. ... gravity is absent in space. Although the planets have gravity, the empty space universe has zero gravity.

you are wrong frnd...

It is a common misconception that rockets are unable to accelerate in space. The fact is that rockets do accelerate. There is indeed nothing for rockets to push off of in space - at least nothing which is external to the rocket. But that's no problem for rockets. Rockets are able to accelerate due to the fact that they burn fuel and push the exhaust gases in a direction opposite the direction which they wish to accelerate.

i sggest you go through the law from your textbook once again..