Consider an elastic collision between a 1-kg block and a 4-kg block. The initial velocity of the 1-kg block is +5 m/s; the 4-kg block is initially at rest. What are the initial velocities of the 1-kg and the 4-kg blocks, respectively, in the center-of-mass reference frame?

Respuesta :

Answer:

4 m/s , - 1 m/s

Explanation:

mass of first block, m1 = 1 kg

mass of second block, m2 = 4 kg

initial velocity of first block, u1 = 5 m/s

initial velocity of second block, u2 = 0 m/s

Let v is the velocity of centre of mass.

The formula used for the velocity of centre of mass is given by

[tex]v=\frac{m_{1}u_{1}+m_{2}u_{2}}{m_{1}+m_{2}}[/tex]

[tex]v=\frac{1\times 5+4\times 0 }{5}[/tex]

v = 1 m/s

So,

the velocity of first block with respect to centre of mass frame = 5 - 1

                                                                                                       = 4 m/s

the velocity of second block with respect to centre of mass frame = 0 - 1

                                                                                                       = -1  m/s

Answer:

The initial velocities of the 1-kg and the 4-kg blocks in the center-of-mass reference frame is 4 m/s and (-1 m/s) respectively.

Explanation:

Given that,

Mass of first block, m = 1 kg

Mass of another block, m' = 4 kg

Initial speed of 1 kg block, u = +5 m/s

Initial speed of 4 kg block, u' = 0 (it was at rest)

Let V is the velocity of the center of mass. It is given by :

[tex]V=\dfrac{mu+m'u'}{m+m'}\\\\V=\dfrac{1\times 5+4\times 0}{1+4}\\\\V=1\ m/s[/tex]

So, the speed of center of mass is 1 m/s

Now, the initial velocity of 1 kg block in the center-of-mass reference frame is,  5 m/s - 1 m/s = 4 m/s

the initial velocity of 4 kg block in the center-of-mass reference frame is,  0 m/s - 1 m/s = -1 m/s

Hence, the initial velocities of the 1-kg and the 4-kg blocks in the center-of-mass reference frame is 4 m/s and (-1 m/s) respectively.