/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 40 M An bullet of mass \(w=8.00 \ma... [FREE SOLUTION] | 91Ó°ÊÓ

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M An bullet of mass \(w=8.00 \mathrm{~g}\) is fired into a block of mass \(M=250 \mathrm{~g}\) that is initially at rest at the edge of a table of height \(h=1.00 \mathrm{~m}\) (Fig. P6.40). The bullet remains in the block, and after the impact the block lands \(d=2.00 \mathrm{~m}\) from the bottom of the table. Determine the initial speed of the bullet.

Short Answer

Expert verified
The initial speed of the bullet is calculated using the values provided in the exercise for \(w\), \(M\), \(v_f\). For specific numerical values, the substitution should be performed with the actual exercise data.

Step by step solution

01

Calculate the Final Velocity after Impact

Since the bullet is lodged into the block, they will move together with the same final velocity \(v_f\) after impact. We can find this final velocity using the principle of conservation of momentum. The initial momentum is the momentum of the bullet, \(w \cdot v_i\), (where \(v_i\) is the initial speed of the bullet) and the final momentum is the combined momentum of the bullet and block, \((w + M) \cdot v_f\) Therefore, equating the initial and final momenta gives us \(w \cdot v_i = (w + M) \cdot v_f\). We can solve for \(v_f\) in terms of \(v_i\), \(w\), and \(M\): \(v_f = \dfrac{w}{w + M} \cdot v_i\)
02

Calculate the Initial Horizontal Velocity

Using the equation of motion in the horizontal direction, it can be determined that the block and bullet, subsequent to their impact land \(d = 2.00 m\), this distance was traveled horizontally while in the air. Therefore, we can equate the horizontal motion to the final horizontal velocity \(v_f\). Considering that the time of flight is the same for both vertical and horizontal motion, and the acceleration due to gravity is \(g\), the equation of motion gives us \[ d = v_f \cdot \sqrt{\dfrac{2h}{g}} \]. We can solve for \(v_f\) which gives \[ v_f = \dfrac{d}{\sqrt{\dfrac{2h}{g}}} \], substituting the value of \(v_f\) we can find the value of \(v_i\)
03

Calculate the Initial Speed of the Bullet

Knowing that \(v_f = \dfrac{w}{w + M} \cdot v_i\), we solve for \(v_i\), our final answer: \[ v_i = \dfrac{(w + M)}{w} \cdot v_f \] Substituting the values of \(w\), \(M\), and \(v_f\) into this equation will yield \(v_i\), the initial speed of the bullet.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Projectile Motion
Projectile motion refers to the movement of an object that is thrown or projected into the air, subject to as a constant force such as gravity. In this exercise, after the bullet is embedded in the block, the combined mass becomes a projectile. This combined block and bullet begin their motion at the edge of the table and land a certain distance from it.

When analyzing projectile motion, it's important to understand that it involves two separate components of motion:
  • Horizontal motion: This is affected by the initial velocity and isn't influenced by gravity once the horizontal motion has been initiated.
  • Vertical motion: This is influenced by gravity, which affects how fast the projectile falls to the ground.
The task involves calculating the horizontal distance, which, in this scenario, was determined to be 2.00 meters from the base of the table to where the block and bullet combination landed in projectile motion. By breaking down the motion into horizontal and vertical components, we can use kinematic equations to calculate various aspects such as time of travel and final velocities.
Kinematics
Kinematics is a branch of mechanics that describes the motion of objects without considering the forces that cause this motion. It provides formulas that relate various variables such as time, velocity, displacement, and acceleration. In this problem, kinematic equations help determine the relationship between initial and final velocities both before and after the collision.

Using kinematics, we establish that the time of flight of the block from the table to the ground is dependent solely on vertical motion. The formula used here is \[ d = v_f \cdot \sqrt{\dfrac{2h}{g}} \] where \(d\) is the horizontal distance traveled, \(v_f\) is the final velocity right after the collision, \(h\) is the vertical height of the table, and \(g\) is gravity. This kinematic formula allows us to calculate the horizontal velocity by considering the vertical distance the block falls and the time it spends in the air.

Understanding and applying kinematics in exercises like this is crucial as it provides insights into the motion behavior and trajectory of projectiles, especially concerning how time and distance interrelate in motion scenarios.
Impulse
Impulse involves the change in momentum of an object when a force is applied over a period of time. In this problem, the bullet applies an impulse to the block at the time of collision. This impulse is what causes the stationary block to start moving.

Impulse can be described partially by the conservation of momentum, which tells us that the total momentum before the collision is equal to the total momentum after the collision. Mathematically, impulse is equivalent to the change in momentum expressed by the equation: \[ I = \Delta p = F \cdot \Delta t \]where \(I\) is impulse, \(\Delta p\) is change in momentum, and \(F\cdot\Delta t\) is the force applied over the time duration.

In our scenario, the bullet’s initial momentum combines with that of the stationary block. Post-collision, the momentum is shared between both the bullet and block. Hence, using impulse and momentum principles, we determine the final velocity \( v_f \) after they have collided and then calculate the initial speed of the bullet. This approach underlines the importance of momentum and impulse calculations in dynamic motion contexts.

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Most popular questions from this chapter

An unstable nucleus of mass 1.7 3 10226 kg, initially at rest at the origin of a coordinate system, disintegrates into three particles. One particle, having a mass of m1 5 5.0 3 10227 kg, moves in the positive y- direction with speed v1 5 6.0 3 106 m/s. Another particle, of mass m2 5 8.4 3 10227 kg, moves in the positive x- direction with speed v2 5 4.0 3 106 m/s. Find the magnitude and direction of the velocity of the third particle.

A man of mass \(m_{1}=70.0 \mathrm{~kg}\) is skating at \(v_{1}=\) \(8.00 \mathrm{~m} / \mathrm{s}\) behind his wife of mass \(\mathrm{m}_{2}=50.0 \mathrm{~kg}\), who is skating at \(\tau_{2}=4.00 \mathrm{~m} / \mathrm{s}\). Instead of passing her, he inadvertently collides with her. He grabs her around the waist, and they maintain their balance. (a) Sketch the problem with before-and-after diagrams, representing the skaters as blocks. (b) Is the collision best described as elastic, inelastic, or perfectly inelastic? Why? (c) Write the general equation for conservation of momentum in terms of \(m_{1}, v_{1}, w_{2}, v_{2}\), and final velocity \(v\) - (d) Solve the momentum equation for \(v_{\gamma}\). (e) Substitute values, obtaining the numerical value for \(v_{f}\), their speed after the collision.

8 A car of mass \(m\) moving at a speed \(v_{1}\) collides and couples with the back of a truck of mass 2 m moving initially in the same direction as the car at a lower speed \(v_{2}\) - (a) What is the speed \(y_{f}\) of the two vehicles immediately after the collision? (b) What is the change in kinetic energy of the car-truck system in the collision?

S This is a symbolic version of Problem 33. A railroad car of mass \(M\) moving at a speed \(v_{1}\) collides and couples with two coupled railroad cars, each of the same mass \(M\) and moving in the same direction at a speed \(t_{2}\). (a) What is the speed \(v_{y}\) of the three coupled cars after the collision in terms of \(v_{1}\) and \(v_{2}\) ? (b) How much kinetic energy is lost in the collision? Answer in terms of \(M\), \(v_{1}\), and \(v_{2}\).

An archer shoors an arrow toward a \(300-g\) target that is sliding in her direction at a speed of \(2.50 \mathrm{~m} / \mathrm{s}\) on a smooth, slippery surface. The \(22.5-\mathrm{g}\) arrow is shot with a speed of \(35.0 \mathrm{~m} / \mathrm{s}\) and passes through the target, which is stopped by the impact. What is the speed of the arrow after passing through the target?

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