Momentum problem (2 Viewers)

[clintmyster]

A Railway truck of mass 2.0 x 10^3 kg moving at 4.5m/s passed under a coal hopper where a load of coal was dumped into it. This caused a reduction of speed to 0.75m/s. What was the mass of the load?

 

[Felix Jones]

momentum=mass*velocity
momentum=2x 10^3x 4.5
=9000

if the momentum remained the same(u didnt say)

9000=mass x 0.75

therefore mass=9000/0.75
=1200kg

 

[Aerath]

I'm not sure you can do it, unless you know p remained constant.

 

[clintmyster]

ive been given an answer of 10x10^3 kg. does that help?

 

[Felix Jones]

can u give me the whole question plz...obviously im missing something...dunno if its my fault or urs.

 

[Dr. Zoidberg]

This is gonna be confusing to explain, but here goes...

m1u1+m2u2=m1v1+m2v2

m1=2.0x10^3
u1=4.5

m2= unknown
u2= 0

v1=0.75
v2=0.75

(2.0x10^3)(4.5)+(m2)(0)=(2.0x10^3)(0.75)+m2(0.75)

9000+0=1500+0.75(m2)

7500=0.75(m2)

m2=10000=10x10^3 kg

 

[lolokay]

can u give me the whole question plz...obviously im missing something...dunno if its my fault or urs.

the question asked for the mass of the load, not truck + load. truck = 2000, truck + load = 12000, so load = 10000.

 

[Arowana21]

GZ....
This is conservation of momentum