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Two persons (each on a skateboard) are initially standing still and facing each other before pushing off of each other. One person (50 kg) moves backwards at 1.1 m/s. Calculate the velocity of the second person (65 kg).

Respuesta :

Answer:

The second person will have a velocity of 0.85 m/s in the opposite direction of the first person.

Explanation:

Law Of Conservation Of Linear Momentum

The total momentum of a system of bodies is conserved unless an external force is applied. The formula for the momentum of a body with mass m and velocity v is:

P=mv.

If we have a system of bodies, then the total momentum is the sum of them all

[tex]P=m_1v_1+m_2v_2+...+m_nv_n[/tex]

If a collision occurs, the velocities change to v' and the final momentum is:

[tex]P'=m_1v'_1+m_2v'_2+...+m_nv'_n[/tex]

In a system of two masses, the law of conservation of linear momentum is:

[tex]m_1v_1+m_2v_2=m_1v'_1+m_2v'_2[/tex]

According to the conditions of the problem, two persons standing on a frictionless surface are initially at rest (v1=0, v2=0). Their masses are m1=50 Kg and m2=65 Kg. After the push, one person (say m1) moves backward at v1'=-1.1 m/s. We can calculate the speed of the other person by solving for v2':

[tex]\displaystyle v'_2=\frac{m_1v_1+m_2v_2-m_1v'_1}{m_2)[/tex]

Substituting:

[tex]\displaystyle v'_2=\frac{50*0+65*0-50(-1.1)}{65)[/tex]

[tex]\displaystyle v'_2=\frac{55}{65}[/tex]

[tex]v'_2=0.85 \ m/s[/tex]

The second person will have a velocity of 0.85 m/s in the opposite direction of the first person.