/*! 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 96 A 20.0-kg projectile is fired at... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

A 20.0-kg projectile is fired at an angle of 60.0\(^\circ\) above the horizontal with a speed of 80.0 m/s. At the highest point of its trajectory, the projectile explodes into two fragments with equal mass, one of which falls vertically with zero initial speed. Ignore air resistance. (a) How far from the point of firing does the other fragment strike if the terrain is level? (b) How much energy is released during the explosion?

Short Answer

Expert verified
The other fragment hits 565.6 m away; energy released is calculated by comparing kinetic before vs vertical kinetic afterward.

Step by step solution

01

Calculate the Initial Horizontal Velocity

The initial velocity of the projectile can be broken down into horizontal and vertical components. Using the angle of projection and initial speed:\[ v_{ix} = v_i \cos(\theta) = 80.0 \times \cos(60.0^\circ) = 40.0 \text{ m/s} \]The initial horizontal velocity \(v_{ix}\) is 40.0 m/s.
02

Calculate the Time to Reach the Highest Point

At the highest point, the vertical component of velocity is zero. Using the vertical motion equation:\[ v_{fy} = v_{iy} - gt \quad \Rightarrow \quad 0 = 80.0 \sin(60.0^\circ) - 9.8t \]Solving for \(t\):\[ t = \frac{80.0 \sin(60.0^\circ)}{9.8} = 7.07 \text{ s} \]
03

Calculate Total Time of Flight

The total time of flight will be twice the time to reach the highest point:\[ T = 2 \times 7.07 = 14.14 \text{ s} \]
04

Find the Distance First Fragment Travels

Since one fragment falls vertically with zero horizontal speed right after the explosion, it does not affect horizontal motion. Let's find the horizontal distance the second fragment travels from the point of explosion to ground.Given the explosion occurs at the highest point which splits the mass, second fragment's horizontal speed remains same, as there are no external horizontal forces:To find the distance traveled by the projectile till explosion:\[ x_{e} = v_{ix} \times 7.07 = 40.0 \times 7.07 = 282.8 \text{ m} \]After the explosion, the second fragment continues moving with the same horizontal velocity \(v_{ix}\) until it hits the ground:Total time from explosion to hitting ground (since launched from highest point, will fall back in same time):\[ 7.07s \]Distance after the explosion:\[ x_{e2} = v_{ix} \times 7.07 = 40.0 \times 7.07 = 282.8 \text{ m} \]The total horizontal range: \[ x_{total} = 282.8 + 282.8 = 565.6 \text{ m} \]
05

Calculate Energy Released During Explosion

Initially, kinetic energy is conserved as only potential energy changes before explosion. At the highest point, potential energy increase equals decrease in initial total energy up there:\[ KE_i = \frac{1}{2}mv_i^2 \]Due to explosion, one fragment stops in vertical course (at max height):Half mass \(m = 10.0 \text{ kg}\):Kinetic Energy of stationary fragment \(KE_1=0\)Second fragment bombs down again (no height advantage):Energy before (Total Particle):New energy (as first is zero now) equals energy stored released due to one being nullified:\[ E_2 = \frac{1}{2} m v_f^2 + mgh\]Potential became true energy release due setting velocity zero:new speed partition also same due initial velocityThus, total potential more that realized pre explosion is energy released:\[ E_{release} = KE_i - E_2 \]
06

Write the Proof Conclusion

We've calculated the different components of the motion and accounted for the explosion scenario, allowing us to summarize the results.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Kinematics
Kinematics is the study of motion without considering the forces that cause it. In projectile motion, we examine how an object moves through space, taking into account initial speed, angles, and acceleration due to gravity.

In this problem, the projectile is fired at an angle of 60 degrees with an initial speed of 80 m/s. This can be resolved into horizontal and vertical components using trigonometric functions:
  • The horizontal velocity is calculated as: \[v_{ix} = v_i imes ext{cos}(60^ ext{o}) = 40 ext{ m/s}\]
  • The vertical velocity is: \[v_{iy} = v_i imes ext{sin}(60^ ext{o}) = 69.28 ext{ m/s}\]

The horizontal motion is uniform since there are no forces acting horizontally, so the velocity remains constant. For vertical motion, gravity acts downwards, decelerating the projectile until it reaches its peak, rendering vertical velocity zero momentarily. The timing related to rise and fall phases of kinematics insights find resonance in this projectile's traversal.
Conservation of Momentum
The conservation of momentum principle states that in a closed system, the total momentum before and after an event remains the same if no external forces act on it.

In the explosion at the highest point of the projectile's path, we consider this principle. The projectile splits into two equal masses, each weighing 10 kg, meaning total mass remains invariant. One fragment falls straight down with no initial horizontal velocity, while the other continues with the initial horizontal speed of 40 m/s.
  • Before the explosion, the momentum is that of the entire projectile, purely horizontal: \[ p_{initial} = m imes v_{ix} = 20 ext{ kg} imes 40 ext{ m/s}\]
  • After the explosion, the momentum is split: \[ 10 ext{ kg} imes 0 + 10 ext{ kg} imes 40 ext{ m/s} \]

Despite splitting, the momentum remains conserved, maintaining continuity in horizontal transit for the still-moving fragment post-explosion.
Energy Conservation
Energy conservation plays a critical role here. Initially, the projectile has kinetic energy due to its velocity, split into components based on the angle of launch.

At the highest point in its trajectory, all vertical kinetic energy converts to potential energy, with only horizontal kinetic energy persisting:
  • Initial kinetic energy (before explosion): \[ KE_i = \frac{1}{2} \times m \times v^2 \]
  • At the highest point: This kinetic energy consists only of horizontal elements since vertical motion halts.
    Post explosion, one fragment ceases its horizontal movement, turning energy void. Replacement of pre-explosion potential becomes apparent in evaluating altered energy states post-decay.
The subtraction of new total kinetic energy from original indicates energy released from the explosion.
Explosions
Explosions dramatically change a system's dynamics, redistributing mass and energy instantaneously.

Here, the projectile divides into two fragments of equal mass. One fragment drops straight down, while the other perpetuates its horizontal route.

The explosion facilitating this separation uses internal energy conversion, typically releasing stored potential via sudden motion or fragmentation:
  • Explosions introduce internal forces, reforming kinetic and potential energies. In our context, post-explosion analyses attest to the energy density changes, visible through how the separate parts of the projectile respond.
  • The energy released is the difference between the initial kinetic energy and energy retained in motion post-split.
By analyzing this problem, understanding the behavior of objects post-explosion enhances insights into directional change and energy transformation during fragmentation scenarios.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Three identical pucks on a horizontal air table have repelling magnets. They are held together and then released simultaneously. Each has the same speed at any instant. One puck moves due west. What is the direction of the velocity of each of the other two pucks?

At time \(t\) = 0 a 2150-kg rocket in outer space fires an engine that exerts an increasing force on it in the \(+x\)-direction. This force obeys the equation \(F_x = At^2\), where \(t\) is time, and has a magnitude of 781.25 N when \(t\) = 1.25 s. (a) Find the SI value of the constant \(A\), including its units. (b) What impulse does the engine exert on the rocket during the 1.50-s interval starting 2.00 s after the engine is fired? (c) By how much does the rocket's velocity change during this interval? Assume constant mass.

A bat strikes a 0.145-kg baseball. Just before impact, the ball is traveling horizontally to the right at 40.0 m/s; when it leaves the bat, the ball is traveling to the left at an angle of 30\(^\circ\) above horizontal with a speed of 52.0 m/s. If the ball and bat are in contact for 1.75 ms, find the horizontal and vertical components of the average force on the ball.

The mass of a regulation tennis ball is 57 g (although it can vary slightly), and tests have shown that the ball is in contact with the tennis racket for 30 ms. (This number can also vary, depending on the racket and swing.) We shall assume a 30.0-ms contact time. The fastest-known served tennis ball was served by "Big Bill" Tilden in 1931, and its speed was measured to be 73 m/s. (a) What impulse and what force did Big Bill exert on the tennis ball in his record serve? (b) If Big Bill's opponent returned his serve with a speed of 55 m/s, what force and what impulse did he exert on the ball, assuming only horizontal motion?

Two figure skaters, one weighing 625 N and the other 725 N, push off against each other on frictionless ice. (a) If the heavier skater travels at 1.50 m/s, how fast will the lighter one travel? (b) How much kinetic energy is "created" during the skaters' maneuver, and where does this energy come from?

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.