Conceptual question regarding net force and velocity

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Homework Help Overview

The discussion revolves around the motion of an object experiencing a net force directed to the right, which is decreasing over time. Participants are exploring the implications of this scenario on the object's velocity and acceleration.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster questions whether an object can increase its speed while experiencing a decreasing net force. They express confusion about the relationship between net force and the object's motion, particularly regarding the possibility of decreasing speed despite a rightward force.

Discussion Status

Some participants have provided insights into the relationship between force, acceleration, and velocity, suggesting that an object can indeed increase its speed even with a decreasing force. However, the original poster is seeking further clarification on why the answer to the problem is not a decrease in speed.

Contextual Notes

The original poster is grappling with the implications of Newton's second law and the effects of changing forces on motion, indicating a need for deeper understanding of these concepts.

physics120
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Homework Statement



An object is moving to the right in a straight line. The net force acting on the object is also directed to the right, but the magnitude of the force is decreasing with time. The object will

a) stop and then begin moving to the left.
b) continue to move to the right, with its speed decreasing with time.
c) continue to move to the right, with its speed increasing with time.
d) continue to move to the right with a constant speed.

The answer is c)

Homework Equations





The Attempt at a Solution



My question is, can an object INCREASE in speed to the right at a DECREASING rate?

If so, then I understand why the answer is c) However, I thought if an object was moving to the right and the net force was also moving to the right, that would mean the object was increasing, and since the net force is decreasing with time, then shouldn't that change how the object is moving? like doesn't that mean the object will begin to decrease in speed?

Please explain to me the reason for the answer! (why it is c, and say, not b)

Thank-you for any help!
 
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physics120 said:
My question is, can an object INCREASE in speed to the right at a DECREASING rate?
Absolutely. As long as it moves to the right and it has an acceleration to the right, it's speed will increase. The rate at which the speed increases depends on the acceleration, which in turn depends on the net force.
 
Newton's second law: F=ma. What happens, if there is a force acting on the object and what happens when you take it off?

DocAl was faster! Damn!
 
Thanks Doc Al!
 

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