Two blocks are free to move on a horizontal frictionless surface. Block A has a

Question

Two blocks are free to move on a horizontal frictionless surface. Block A has a mass m = 2kg and is initially moving to the right with a speed of v = 5m/s. Block B has a mass of m = 6kg and is initially not moving.

6)  If the blocks collide and stick together, what is the final velocity of the two blocks?

vf = 1.25 m/s

vf = 1.75 m/s

vf = 2.00 m/s

7)  If two blocks collide elastically (bounce off) what is the final velocity of block A?

v = 2.0 m/s to the left

v = 2.5 m/s to the left

v = 2.0 m/s to the right

v = 2.5 m/s to the right

8)  If two blocks collide elastically (bounce off) what is the final velocity of block B

v = 2.0 m/s to the left

v = 2.5 m/s to the left

v = 2.0 m/s to the right

v = 2.5 m/s to the right

Explanation / Answer

step;1

Given that

mass m1=M

mass m2=3M

initial speed u1=5 m/s

initial speed u2=0 m/s

step;2

now we find the finial velocity both block are strick

according to law of conservation of momentum

m1u1+m2u2=(m1+m2)v

M*5+3M*0=[M+3M]v

finial velocity V=5M/4M=1.25 m/s

step;3

now we find the velocity of block A

velocity of block A=>Vf=(m1-m2)u1/(m1+m2)+2m2u2/(m1+m2)

=(M-3M)5/(M+3M)+2*3M*0/(M+3M)

=-2.5 m/s

the velocity of block A is 2.5 m/s left

step;4

now we find the velocity of block Bafter collision

velocity of block B=2m1u1/(m1+m2)+(m2-m1)u2/(m1+m2)

=2*M*5/(M+3M)+0

=2.5 to right

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