Solving Collision Problems: Engine and Carriage Homework Questions

[flarefiragax]

Homework Statement

A single runaway train engine with a mass of 10 000kg is traveling at 15 m/s. The runaway engine collides and joins with a stationary carriage of 5000kg, which as not had brakes applied. After an impact of 0.5s, the engine and carriage then continue along the track as one.

a) What is the speed of the joined engine and carriage after the collision?

b) What is the magnitude of the change in momentum of the carriage during the collision?

c) What is the magnitude of the impulse applied to the carriage during the 0.5s collision?

d) What is the magnitude of the force acting on the engine during the collision?

I think this question assumes that air resistance and friction on the rail are negligible

Homework Equations

The Attempt at a Solution

I have no idea where to start :S

Help please :D

 

[rock.freak667]

Start with applying conservation of momentum to find the speed after the collision

momentum before collision = momentum after the collsion

 

[flarefiragax]

Oh okay so.

a) Total momentum before collision = momentum after collision

Momentum before collision:

= 10,000 * 15 + 5000 * 0

= 150, 000 kgms-1

Momentum after collision:

(10, 000 + 5000)* = 15000 v

v = velocity after collision

Since momentum is conserved.

15, 000*v = 150, 000

v = 150, 000/15, 000

v = 10 m/s

Is that the right answer?

How do I do the b, c, d?

Thanks so much! :D

 

[rock.freak667]

Oh okay so.

a) Total momentum before collision = momentum after collision

Momentum before collision:

= 10,000 * 15 + 5000 * 0

= 150, 000 kgms-1

Momentum after collision:

(10, 000 + 5000)* = 15000 v

v = velocity after collision

Since momentum is conserved.

15, 000*v = 150, 000

v = 150, 000/15, 000

v = 10 m/s

Is that the right answer?

That should be right.

How do I do the b, c, d?

So we know that both the carriage and engine are moving at 10m/s after collision.

The initial momentum of the carriage is 10,000 * 15.

What is the final momentum if the carriage?

The change would just be the difference between these two.

For part c: How is impulse and change in momentum related?

for part d: Think of Newton's 2^nd Law