work and energy and impulse and momentum?

Question

1. A 10 kg bix,initially at rest, is pulled through a distance of 8 m across a level floor by a 10 N force applied parallel to the floor.The coeffcient of friction between the floor and the box is 0.25
a. what is the work done by the force ?
b. what is the work done by friction?
c. what is the network on the box?
d. what is the speed of the box at the end of 5 m?

2.Two bodies of masses 2 kg and 4 kg moving with velocities of 10 m/s, east and 20 m/s west respectively,collide head on.
a. what is the total momentum of the bodies before collision ?
b. if the collision perfectly inelastic,what is the velocity of the bodies after collision?
c. if the collision is perfectly elastic,what is the velocity of the 2 kg and 4 kg ball after collision?

please kindly help me with dis problem
a BIG THANKS

sorry, i mean for bix is BOX

Answer 1

check your source data bix!

chico I don’t mean spelling; I do mean numbers!
a♠ total momentum M= m1*v1+m2*v2 = 2*10 –4*20 = -60 kg m/s;
for (b) and (c) M is conserved after collision that is: M= m1*v3 +m2*v4;
b♣ inelastic means they stuck to each other thus moving with the same v4=v3=v;
therefore M=-60 =m1*v +m2*v =2*v +4*v, hence v= -10 m/s (minus for west!);
c♦ also energy is conserved, that is E = 0.5m1*v1^2 +0.5m2*v2^2 = 0.5m1*v3^2 +0.5m2*v4^2; therefore 2*10^2 +4*20^2 = 2*v3^2 +4*v4^2, hence
200+1600 = 2*v3^2 +4*v4^2, while –60 =2*v3 +4*v4; 2 equations!
• v3^2 +2*v4^2 =900;
• v3 +2*v4 =-30;
♥ solving them: case1 v3=-30, v4=0, insert into equations – OK!
case2 v3=10, v4=-20, insert into equations – OK, but this was before collision!;
thus after collision 4kg body stands, 2kg body moves to the west at 30 m/s;

Answer 2

impulse = exchange in momentum ball's exchange in momentum (preliminary vel= 0)= (mass)(very final velocity)= 0.046(40) = a million.80 4 kg-m/s impulse = a million.80 4 N-s ANS (a) a million.80 4/0.020 = ninety two N ANS (b)

Answer 3

friction =0.25x10xg=24.5 newton hence applied force will not be able to move the body
answer to all parts is zero