Question

A 7.0-kg shell at rest explodes into two fragments, one with a mass of 2.0 kg and the other with a mass of 5.0 kg. If the heavier fragment gains 100 J of kinetic energy from the explosion, how much kinetic energy does the lighter one gain?

Answer 1

Answer:

39.94m/s.

Explanation:

Kinetic energy is expressed as KE = 1/2 mv² where;

m is the mass of the body

v is the velocity of the body.

For the heavier shell;

m = 5kg

KE gained = 100J

Substituting this values into the formula above to get the velocity v;

100 = 1/2 * 5 * v²

5v² = 200

v² = 200/5

v² = 40

v = √40

v = 6.32 m/s

Note that after the explosion, both body fragments will possess the same velocity.

For the lighter shell;

mass = 2.0kg and v = 6.32m/s

KE of the lighter shell = 1/2 * 2 * 6.32²

KE of the lighter shell = 6.32²

KE of the lighter shell= 39.94m/s

Hence, the lighter one gains a kinetic energy of 39.94m/s.

Answer 2

The gain in the kinetic energy of the smaller fragment is 249.64 J.

The given parameters;

• Mass of the shell, m = 7.0 kg
• Mass of one fragment, m₁ = 2.0 kg
• Mass of the second fragment, m₂ = 5.0 kg
• Kinetic energy of heavier fragment, K.E₁ = 100 J

The velocity of the heavier fragment is calculated as follows;

$K.E = \frac{1}{2} mv^2\\\\mv^2 = 2K.E\\\\v^2 = \frac{2K.E}{m} \\\\v= \sqrt{\frac{2K.E}{m} } \\\\v = \sqrt{\frac{2 \times 100}{5} }\\\\v = 6.32 \ m/s$

Apply the principle of conservation of linear momentum to determine the velocity of the smaller fragment as;

$m_1 u_1 + m_2 u_2 = v(m_1 + m_2)\\\\-6.32(5) \ + 2u_2 = 0(7)\\\\-31.6 + 2u_2 = 0\\\\2u_2 = 31.6\\\\u_2 = \frac{31.6}{2} \\\\u_2 = 15.8 \ m/s$

The gain in the kinetic energy of the smaller fragment is calculated as follows;

$K.E_2 = \frac{1}{2} mu_2^2\\\\K.E_2 = \frac{1}{2} \times 2 \times (15.8)^2\\\\K.E_2 = 249.64 \ J$

Thus, the gain in the kinetic energy of the smaller fragment is 249.64 J.

Learn more about conservation of linear momentum here: https://brainly.com/question/7538238