Two bodies of mass 1kg and 2kg respectively moving in the directions opposite to each other with a speed 5m/s collide. Calculate the total momentum of the system before collision.

Please solve it answer is
-4kgm/s

Two bodies of mass 1 kg and 2kg respectively moving in the direction opposite to each other with speed V metre per second collides calculate the total momentum of the system before collision

minus 4 kg metre per second

2nd of mass 1kg and 2kg respect leave moving in a direction of opposite to each other with a speed of 5 metre per second Clyde calculate the total momentum of the system before collision

But in book the answer is quite different it is given as - 4 kg metre per second

Loda

A bullet  of mass 10g is fired at a speed of 400m/s from a gun of mass 4 kg. what is the recoil velocity of the gun?
Ans= For bullet,
mass {m1}=10g=10/1000=0.01kg
final velocity{v1}=400m/s
initial velocity{u1}=0m/s
Now,for gun
mass {m2}=4kg
final velocity{v2}=?
initial velocity{u2}=0m/s
Recoil velocity of gun,
total initial momentum = total final momentum
m1u1+m2u2=m1v1+m2v2
0.01(0)+4(0)=0.01(400)+4(v2)
0+0=4+4(v2)
-4(v2)=4
-v2=4/4
-v2=1
v2= -1m/s
Here the negative sign indicates the recoil velocity of the gun tat is 1m/s