Freight Wagons Collision: Calculating Speed, Acceleration & Force

[ollieman]

Homework Statement

An empty freight wagon of mass 10000kg rolls at 2.0 ms-1 along a level track and collides with a loaded wagon with a mass of 15000kg standing at rest with its breaks realized, If the wagons join together find.

a. their joint speed after the collision.

b. if the collision takes place in 0.1 seconds, what was the acceleration of the moving wagon during the collision

c. what was unbalanced force on the moving wagon during the collision?

d. What was the force on the moving wagon on the stationary wagon?

The Attempt at a Solution

I'm pretty sure the first question uses the law of conservation of momentum

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

But i am just lost with what i need to substitute into this equation :(

 

[LowlyPion]

Homework Statement

An empty freight wagon of mass 10000kg rolls at 2.0 ms-1 along a level track and collides with a loaded wagon with a mass of 15000kg standing at rest with its breaks realized, If the wagons join together find.

a. their joint speed after the collision.

b. if the collision takes place in 0.1 seconds, what was the acceleration of the moving wagon during the collision

c. what was unbalanced force on the moving wagon during the collision?

d. What was the force on the moving wagon on the stationary wagon?

The Attempt at a Solution

I'm pretty sure the first question uses the law of conservation of momentum

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

But i am just lost with what i need to substitute into this equation :(

Welcome to PF.

So what kid of collision do you think this is?
Elastic?
Or inelastic?

 

[ollieman]

Welcome to PF.

So what kid of collision do you think this is?
Elastic?
Or inelastic?

Thanks for replying to my post LowlyPion

i haven't got any idea, it would be the most basic. Since this is my first year studying physics in a physical science course

 

[LowlyPion]

Thanks for replying to my post LowlyPion

i haven't got any idea, it would be the most basic. Since this is my first year studying physics in a physical science course

In the equation you provided, any idea about what the terms are?

 

[ollieman]

$$\sum$$ P_i = $$\sum$$ P_f

From Newtons second law

 

[LowlyPion]

I understand what Conservation of momentum is thanks.

I was asking you what the terms were in the equation you wrote? What is m1 and u1 and ... etc.

 

[ollieman]

My text just says i can use either

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

or

$$\sum$$ P_i = $$\sum$$ P_f

 

[LowlyPion]

My text just says i can use either

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

or

$$\sum$$ P_i = $$\sum$$ P_f

Yes the first is the two body form of the second.

Now what is m1 and m2 ?
What is u1 and u2 and v1 and v2?

 

[ollieman]

m1 mass of the first object
m2 mass of the second object
u1 initial velocity of the first object
u2 initial velocity of the second object
v1 final velocity of the first object
v2 final velocity of the first object

Sorry i just thought it was how it worked, but it must be only how I'm taught

 

[LowlyPion]

m1 mass of the first object
m2 mass of the second object
u1 initial velocity of the first object
u2 initial velocity of the second object
v1 final velocity of the first object
v2 final velocity of the first object

Sorry i just thought it was how it worked, but it must be only how I'm taught

There you go. Good.

Now look at your problem and start assigning values. (Remember since it is inelastic you will have both final velocities equal.)

 

[ollieman]

I couldn't get it out right :s that's why i posted it on here

 

[LowlyPion]

I couldn't get it out right :s that's why i posted it on here

They give you the mass of the 2 wagons. What do you figure those are then in the equation?

Plug them in.

The velocity of one of the wagons is given. Plug that in.

Then solve for the final velocity.