Skip to main content
Ch 09: Work and Kinetic Energy
Chapter 9, Problem 9

A red ball has a mass of 250 g. A constant force pushes the red ball horizontally and launches it at a speed of 15 m/s . The same force pushes a green ball through the same distance, launching it at 25 m/s. What is the mass of the green ball?

Verified Solution

Video duration:
6m
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Newton's Second Law of Motion

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This relationship is expressed by the formula F = ma, where F is the force, m is the mass, and a is the acceleration. Understanding this law is crucial for analyzing how different masses respond to the same force.
Recommended video:
Guided course
06:54
Intro to Forces & Newton's Second Law

Kinetic Energy

Kinetic energy is the energy an object possesses due to its motion, calculated using the formula KE = 1/2 mv², where m is the mass and v is the velocity. In this problem, the kinetic energy of both balls can be compared to understand how the different speeds relate to their masses when acted upon by the same force.
Recommended video:
Guided course
06:07
Intro to Rotational Kinetic Energy

Conservation of Energy

The principle of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. In this scenario, the work done by the constant force on both balls translates into kinetic energy, allowing us to set up equations that relate the forces, distances, and resulting speeds to find the unknown mass of the green ball.
Recommended video:
Guided course
06:24
Conservation Of Mechanical Energy