A railway carriage of mass 10000kg moving with a speed 15/s hits a stationary carriage of same mass. after the collision the carriage get coupled and ove together. what is their common velocity after collision?

2 Answers
Jan 27, 2018

7.5ms^-17.5ms1

Explanation:

So the formula for linear momentum, rhoρ, is rho=mvρ=mv.

So before the collision, the momentum of the system is 10000*15=150000kgms^-11000015=150000kgms1.

After the collision, the momentum, according to the law of conservation of momentum, remains the same. That is, rho_1=rho_2ρ1=ρ2, or m_1v_1=m_2v_2m1v1=m2v2

Here, v_2=(m_1v_1)/m_2v2=m1v1m2

m_1v_1=150000m1v1=150000, we know this from our prior calculations. Now, since the second carriage gets stuck to the first one, the mass of the system, m_2m2, is equal to 20000kg20000kg

v_2=150000/20000v2=15000020000

v_2=7.5ms^-1v2=7.5ms1

Jan 27, 2018

=7.5"m/s"=7.5m/s

Explanation:

Applying the Law of Conservation of Momentum, identify the given data and set-up the needed formula to determine the common velocity of the carriages after the collision.

"Momentum before" (P_("before"))="Momentum after"(P_(after))Momentum before(Pbefore)=Momentum after(Pafter)

where:where:

"Momentum(P)"="mass(m)"xx"velocity(v)"Momentum(P)=mass(m)×velocity(v)
P=mvP=mv

(P_("before")):(Pbefore):
The masses and the velocities of the carriages before the collision

m_1=10,000kg; v_1="15m/s"m1=10,000kg;v1=15m/s
m_2=10,000kg; v_2="0m/s " ( "at rest")m2=10,000kg;v2=0m/s (at rest)

(P_(after)):(Pafter):
The masses and the velocities of the carriages after the collision

m_1=10,000kg; v_1'=?
m_2=10,000kg; v_2'=?

Take note that after the collision, both carriages moved together of same direction with the moving carriage. So that, a common velocity has been identified as follows:

v_1'=v_2'=v_c="common velocity"

Now, set-up the equation and plug in values in both conditions: before and after the collisions as described below.

P_("before")=P_(after)

m_1v_1+m_2v_2=m_1v_1'+m_2v_2'

but:

v_1'=v_2'=v_c

m_1v_1+m_2v_2=m_1v_c'+m_2v_c'

(10,000kg)("15m/s")+cancel((10,000kg)("0m/s"))0=(10,000kg)(v_c)+(10,000kg)(v_c)

150,000"kg.m/s"+0=(20,000kg)v_c; divide both sides by 20,000kg to isolate the variable v_c

v_c=(150,000cancel(kg)."m/s")/(20,000cancel(kg))

v_c=7.5"m/s"