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A 1500-kg car moving east at \(17 \mathrm{m} / \mathrm{s}\) collides with a 1800-\(\mathrm{kg}\) car moving south at \(15 \mathrm{m} / \mathrm{s}\) and the two cars stick together. (a) What is the velocity of the cars right after the collision? (b) How much kinetic energy was converted to another form during the collision?

Short Answer

Expert verified
After the collision, the cars' velocity is 11.26 m/s at an angle of 46.9° south of east. The amount of kinetic energy converted to another form during the collision is 209,288.4 J.

Step by step solution

01

Calculate the initial momenta of both cars

First, we can find the initial momentum of both cars, before the collision. We can use the formula for momentum: \(p=mv\), where \(p\) is the momentum, \(m\) is the mass, and \(v\) is the velocity. Car 1 (1500 kg): \(p_1 = m_1v_1 = 1500\,\text{kg} \times 17\,\text{m/s} = 25500\,\text{kg}\,\text{m/s}\) Car 2 (1800 kg): \(p_2 = m_2v_2 = 1800\,\text{kg} \times 15\,\text{m/s} = 27000\,\text{kg}\,\text{m/s}\)
02

Step 2:The conservation of linear momentum

According to the conservation of linear momentum, the total momentum before the collision should be equal to the total momentum after the collision. Since both of the cars are moving in different directions, we need to consider the momentum conservation in both the x and y directions separately. Total initial momentum in x-direction (east): \(p_{1x} = 25500\,\text{kg}\,\text{m/s}\) Total initial momentum in y-direction (south): \(p_{2y} = 27000\,\text{kg}\,\text{m/s}\) Total mass after the collision: \(m_{tot} = m_1 + m_2 = 1500\,\text{kg} + 1800\,\text{kg} = 3300\,\text{kg}\) Since the total initial momentum should be equal to the total final momentum, we can find the final velocity components by dividing the initial momentum components by the total mass: \(v_{fx} = \frac{p_{1x}}{m_{tot}} = \frac{25500\,\text{kg}\,\text{m/s}}{3300\,\text{kg}} = 7.73\,\text{m/s}\) \(v_{fy} = \frac{p_{2y}}{m_{tot}} = \frac{27000\,\text{kg}\,\text{m/s}}{3300\,\text{kg}} = 8.18\,\text{m/s}\)
03

Calculate the final velocity

To find the final velocity after the collision, we need to combine the final velocity components found in the previous step. We can use the Pythagorean theorem to find the magnitude of the final velocity, and calculate the angle with respect to the x-axis (east) using trigonometry. \(v_{f} = \sqrt{v_{fx}^2 + v_{fy}^2} = \sqrt{(7.73\,\text{m/s})^2 + (8.18\,\text{m/s})^2} = 11.26\,\text{m/s}\) \(\theta_f = \text{tan}^{-1}\frac{v_{fy}}{v_{fx}} = \text{tan}^{-1}\frac{8.18\,\text{m/s}}{7.73\,\text{m/s}} = 46.9^{\circ}\) So the final velocity right after the collision is \(11.26\,\text{m/s}\) at an angle of \(46.9^{\circ}\) south of east.
04

Calculate the initial and final kinetic energies

To find how much kinetic energy was converted to another form, we need to calculate the initial and final kinetic energies. Initial kinetic energies: \(KE_1 = \frac{1}{2}m_1v_1^2 = \frac{1}{2}(1500\,\text{kg})(17\,\text{m/s})^2 = 217125\,\text{J}\) \(KE_2 = \frac{1}{2}m_2v_2^2 = \frac{1}{2}(1800\,\text{kg})(15\,\text{m/s})^2 = 202500\,\text{J}\) Final kinetic energy: \(KE_f = \frac{1}{2}m_{tot}v_f^2 = \frac{1}{2}(3300\,\text{kg})(11.26\,\text{m/s})^2 = 210336.6\,\text{J}\)
05

Calculate the converted kinetic energy

Finally, to find the converted kinetic energy, we can subtract the final kinetic energy from the initial kinetic energies. Converted kinetic energy = \((KE_1 + KE_2) - KE_f = (217125\,\text{J} + 202500\,\text{J}) - 210336.6\,\text{J} = 209288.4\,\text{J}\) Hence, \(209288.4\,\text{J}\) of kinetic energy was converted to another form during the collision.

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