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A 0.45 kg spike is hammered into a railroad tie. The initial speed of the spike is equal to1.9 m/s.If the tie and spike together absorb 22 per- cent of the spike’s initial kinetic energy as internal energy, calculate the increase in in- ternal energy of the tie and spike.Answer in units of J.

Sagot :

Given:

mass of the spike is

[tex]0.45\text{ kg}[/tex]

initial speed od the spike is

[tex]v_=\text{ 1.9 m/s}[/tex]

if the tie and spike together absorb 22 percent of the spike's initial kinetic energy.

Required:

calculate the increase in internal energy of the tie and spike.

Explanation:

here we apply conservation of energy.

[tex]\Delta U+\Delta K+\Delta P=0[/tex]

total change in energy is zero.

here potential energy is not given so neglect that part. we have only

[tex]\Delta U+\Delta K=0[/tex][tex]\Delta U=-\Delta K[/tex]

Here,

[tex]\Delta U=-(K_2-K_1)[/tex]

K1 is initial kinetic energy and K2 is final kinetic energy that is equal to zero.

now we have

[tex]\Delta U=K_1[/tex]

we know that kinetic energy is

[tex]K=\frac{1}{2}mv^2[/tex]

then

[tex]\Delta U=\frac{1}{2}mv^2[/tex]

plugging all the values in the above relation. we get

[tex]\begin{gathered} \Delta U=\frac{1}{2}\times0.45\text{ kg }\times(1.9\text{ m/s})^2\times0.22 \\ \Delta U=0.18\text{ J} \end{gathered}[/tex]

Thus, the change in internal energy is

[tex]0.18\text{ J}[/tex]