AS Physics Linear Momentum Question

In summary, the lorry and car have momentums of 400,000Ns and 27,000Ns respectively before impact. The total momentum is the sum of these values, which remains the same before and after the collision. The textbook answer of 427kNs may be an error.
  • #1
seiei
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Homework Statement


A lorry of mass 20,000kg is traveling at 20.0m/s towards a car of mass 900kg traveling at 30m/s towards the lorry. What is the magnitude of the total momentum?


Homework Equations


m1u1+m2u2=p1
Not sure about any others :\

The Attempt at a Solution


The lorry has a momentum of 400,000Ns in the positive direction and the car has a momentum of 27000Ns in the negative direction but this is before impact. Not sure how to go about this, any help would be appreciated.
 
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  • #2
welcome to pf!

hi seiei! welcome to pf! :smile:

(try using the X2 icon just above the Reply box :wink:)
seiei said:
The lorry has a momentum of 400,000Ns in the positive direction and the car has a momentum of 27000Ns in the negative direction but this is before impact.

That's fine :smile: … what's worrying you about that? :confused:

The total https://www.physicsforums.com/library.php?do=view_item&itemid=53" is just the sum (400000 - 27000), and it's the same before as after the collision anyway …

momentum (and https://www.physicsforums.com/library.php?do=view_item&itemid=313")
 
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  • #3


tiny-tim said:
hi seiei! welcome to pf! :smile:

(try using the X2 icon just above the Reply box :wink:)


That's fine :smile: … what's worrying you about that? :confused:

The total https://www.physicsforums.com/library.php?do=view_item&itemid=53" is just the sum (400000 - 27000), and it's the same before as after the collision anyway …

momentum (and https://www.physicsforums.com/library.php?do=view_item&itemid=313")

Oh right, I'll remember that for next time :D! Yeah I thought the answer was 373kNs but the textbook answer said 427kNs... I was getting kinda confused. Anyways, it's probably just an error in the answers so I'll tell my teacher about that, thanks for the help!
 
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What is linear momentum in physics?

Linear momentum is a measure of the motion of an object, taking into account both its mass and velocity. It is a vector quantity, meaning it has both magnitude and direction. In simple terms, it describes how much an object is moving and in what direction.

How is linear momentum calculated?

Linear momentum (p) is calculated by multiplying an object's mass (m) by its velocity (v): p = m * v. The SI unit of momentum is kilogram-meter per second (kg•m/s).

What is the law of conservation of linear momentum?

The law of conservation of linear momentum states that in a closed system, the total linear momentum of the system remains constant. This means that the total momentum before an interaction or event is equal to the total momentum after.

How is the principle of linear momentum applied in real life?

The principle of linear momentum is applied in many real-life situations, such as in sports like football or hockey, where players use their momentum to gain speed or change direction. It is also important in transportation, as the momentum of a moving vehicle can affect its ability to stop or turn.

What are some common misconceptions about linear momentum?

One common misconception is that linear momentum is the same as velocity. While velocity is a component of momentum, it is not the same thing. Another misconception is that momentum is only important for large or fast-moving objects, when in reality, all objects have momentum and it can be a crucial factor in determining their behavior.

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