Skip to main content
Ch 11: Impulse and Momentum
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 11, Problem 8

A 2.0 kg object is moving to the right with a speed of 1.0 m/s when it experiences the force shown in FIGURE EX11.8. What are the object's speed and direction after the force ends?

Verified step by step guidance
1
Identify the given values: The mass of the object is 2.0 kg, the initial velocity is 1.0 m/s to the right, and the force as a function of time is provided in the figure (assume the force-time graph is available). The goal is to find the final speed and direction of the object after the force ends.
Determine the impulse imparted to the object by the force. Impulse is the integral of force over time: \( J = \int F(t) \, dt \). Use the force-time graph to calculate the area under the curve, as this represents the impulse.
Relate impulse to the change in momentum using the impulse-momentum theorem: \( J = \Delta p \), where \( \Delta p = m \cdot \Delta v \). Solve for the change in velocity: \( \Delta v = \frac{J}{m} \).
Determine the final velocity of the object: \( v_f = v_i + \Delta v \), where \( v_i \) is the initial velocity. Use the sign of \( \Delta v \) to determine whether the object is still moving to the right or has reversed direction.
Finally, calculate the magnitude of the final speed (absolute value of \( v_f \)) and specify the direction based on the sign of \( v_f \). If \( v_f > 0 \), the object is moving to the right; if \( v_f < 0 \), it is moving to the left.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
7m
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 net force, m is the mass, and a is the acceleration. Understanding this law is crucial for analyzing how the force affects the object's motion.
Recommended video:
Guided course
06:54
Intro to Forces & Newton's Second Law

Momentum

Momentum is defined as the product of an object's mass and its velocity, represented by the equation p = mv. It is a vector quantity, meaning it has both magnitude and direction. The conservation of momentum principle states that in a closed system, the total momentum before and after an event remains constant, which is essential for determining the object's speed and direction after the force is applied.
Recommended video:
Guided course
05:17
Intro to Momentum

Kinematics

Kinematics is the branch of mechanics that deals with the motion of objects without considering the forces that cause the motion. It involves concepts such as displacement, velocity, and acceleration. In this scenario, kinematic equations can be used to calculate the final speed and direction of the object after the force has acted on it, based on its initial conditions and the effects of the force.
Recommended video:
Guided course
08:25
Kinematics Equations