/*! 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 56 As a protest against the umpire'... [FREE SOLUTION] | 91Ó°ÊÓ

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As a protest against the umpire's calls, a baseball pitcher throws a ball straight up into the air at a speed of \(20.0 \mathrm{~m} / \mathrm{s}\). In the process, he moves his hand through a distance of \(1.50 \mathrm{~m}\). If the hall has a mass of \(0.150 \mathrm{~kg}\), find the force he exerts on the ball to give it this upward speed.

Short Answer

Expert verified
The pitcher exerts a force of \(10 \mathrm{N}\) on the ball.

Step by step solution

01

Identify the initial velocity, final velocity, and distance

According to the problem, the initial velocity (u) of the ball is 0 m/s, the final velocity (v) is 20 m/s, and the distance through which the pitcher moves his hand (s) is 1.50 m.
02

Use the equation of motion

Let's use the third equation of motion \(v^2 = u^2 + 2as\) to find the acceleration. According to this equation, \(20^2 = 0^2 + 2*a*1.5\). Solving for \(a\), we find that the acceleration (a) is \(200/3 \mathrm{m/s}^2\).
03

Use Newton's second law

According to Newton's second law, force (F) equals mass (m) multiplied by acceleration (\(a\)). In this case, \(F = m*a\). Substituting the given mass (0.150 kg) and the calculated acceleration (\(200/3 \mathrm{m/s}^2\)), we find that the pitcher exerts a force of \(10 \mathrm{N}\) on the ball to give it an upward speed of \(20 \mathrm{m/s}\).

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Key Concepts

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

Equations of Motion
Understanding equations of motion is essential for solving problems involving the movement of objects. They describe the relationship between an object's velocity, acceleration, distance traveled, and time taken. In the given exercise, we deal with an object, a baseball, being thrown vertically upward.

We used the third equation of motion, which is expressed as \(v^2 = u^2 + 2as\), where \(v\) represents the final velocity, \(u\) the initial velocity, \(a\) the acceleration, and \(s\) the distance covered. These equations are derived from the constant acceleration formulas and are extremely helpful for evaluating the motion of objects when the acceleration is constant, as in the case of gravity acting on the baseball.

To solve the problem, we substituted the known values into the third equation to find the acceleration. The initial velocity (when the pitcher starts to move his hand) is zero and the final velocity is given as \(20.0 \mathrm{~m/s}\), with a displacement of \(1.50 \mathrm{~m}\). Understanding and appropriately applying equations of motion can efficiently help us determine missing variables in similar physics problems.
Newton's Second Law
Newton's second law of motion is a cornerstone of classical mechanics and can be succinctly stated as \(F=ma\), where \(F\) is the force applied to an object, \(m\) is the object's mass, and \(a\) is its acceleration. The law essentially tells us that the force exerted on an object is directly proportional to the acceleration it experiences and is also directly proportional to the object's mass.

In the context of the baseball problem, after determining the ball's acceleration using the equations of motion, we applied Newton's second law to find the force. By plugging the mass of the ball and the computed acceleration into the formula, we were able to calculate that the pitcher exerted a force of \(10 \mathrm{N}\) to reach a final velocity of \(20 \mathrm{m/s}\) over a displacement of \(1.50 \mathrm{m}\).

This law is pivotal for understanding how forces affect the motion of objects and is particularly useful for exploring the dynamics of objects in various scenarios, including the vertical motion of objects under the influence of gravity or the forces exerted in a game of baseball.
Kinematics
Kinematics is the branch of physics concerned with the motion of objects without considering the forces that cause this motion. It provides us with the tools to describe an object's position, speed, velocity, and acceleration over time. Key kinematic quantities include displacement, time, velocity, and acceleration, which are interconnected by kinematic equations.

When analyzing the problem of the baseball's vertical throw, kinematics allows us to predict subsequent motion of the ball after being subjected to a force. It involves understanding the initial conditions of the ball's movement and how these conditions are transformed into its velocity and position over the duration of its flight.

Kinematic equations are vital for comprehending the motion of objects launched or thrown in various contexts, such as sports or celestial bodies moving in space. Knowing how to interpret and apply these equations is an invaluable skill when venturing into more complex areas of physics.

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Most popular questions from this chapter

(a) An clevator of mass \(m\) moving upward has two forces acting on it: the upward force of tension in the cable and the downward force due to gravity. When the elevator is accelerating upward, which is greater, \(T\) or \(w ?^{2}\) (b) When the elevator is moving at a constant velocity upward, which is greater, \(T\) or \(w ?\) (c) When the elevator is moving upward, but the acceleration is downward, which is greater, Tor w? (d) Let the elevator have a mass of \(1500 \mathrm{~kg}\) and an upward acceleration of \(2.5 \mathrm{~m} / \mathrm{s}^{2}\), Find \(T\). Is your answer consistent with the answer to part (a)? (e) The elevator of part (d) now moves with a constant upward velocity of \(10 \mathrm{~m} / \mathrm{s}\). Find \(T\). Is your answer consistent with your answer to part (b)? (f) Having initially moved upward with a constant velocity, the elevator begins to accelerate downward at \(1.50 \mathrm{~m} / \mathrm{s}^{2}\), Find \(T\). Is your answer consistent with your answer to part (c)?

A hockey puck struck by a hockey stick is given an initial speed \(v_{0}\) in the positive \(x\) -direction. The coefficient of kinetic friction between the ice and the puck is \(\mu_{k^{\prime}}\) (a) Obtain an expression for the acceleration of the puck. (b) Use the result of part (a) to obtain an expression for the distance \(d\) the puck slides. The answer should be in terms of the variables \(v_{0}, \mu\), and \(g\) only.

The parachute on a race car of weight \(8.820 \mathrm{~N}\) opens at the end of a quarter-mile run when the car is traveling at \(35 \mathrm{~m} / \mathrm{s} .\) What total retarding force must be supplied by the parachute to stop the car in a distance of \(1000 \mathrm{m?}\)

A \(1000-\mathrm{kg}\) car is pulling a \(300-\mathrm{kg}\) trailer. Together, the car and trailer have an acceleration of \(2.15 \mathrm{~m} / \mathrm{s}^{2}\) in the forward direction. Neglecting frictional forces on the trailer, determine (a) the net force on the car, (b) the net force on the trailer, (c) the force exerted by the trailer on the car, and (d) the resultant force exerted by the car on the road.

A coin is placed near one edge of a book lying on a table, and that edge of the book is lifted until the coin just slips down the incline as shown in Figure \(\mathrm{P} 4,70\). The angle of the incline, \(\theta_{c}\), called the critical angle, is measured. (a) Draw a frec-body diagram for the coin when it is on the verge of slipping and identify all forces acting on it. Your free- body diagram should include a force of static friction acting up the incline. (b) Is the magnitude of the friction force equal to \(\mu_{3} n\) for angles less than \(\theta_{c}\) ? Explain. What can you definitely say about the magnitude of the friction force for any angle \(\theta \leq \theta_{c} ?\) (c) Show that the coefficient of static friction is given by \(\mu_{\mathrm{s}}=\tan \theta_{c}\). (d) Once the coin starts to slide down the incline, the angle can be adjusted to a new value \(\theta_{c}^{\prime} \leq \theta_{c}\) such that the coins moves down the incline with constant speed. How does observation enable you to obtain the coefficient of kinetic friction?

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