Conceptual question regarding net force and velocity

In summary, an object moving to the right in a straight line with a net force also directed to the right will continue to move to the right, with its speed increasing with time, if the magnitude of the force is decreasing with time. This is because the acceleration of the object is still to the right, causing its speed to increase at a decreasing rate. This is in accordance with Newton's second law, where the force and acceleration are directly proportional.
  • #1
physics120
34
0

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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  • #2
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.
 
  • #3
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!
 
  • #4
Thanks Doc Al!
 

What is net force?

Net force is the sum of all forces acting on an object. It is a vector quantity, meaning it has both magnitude and direction. In other words, it is the overall force that is causing an object to accelerate or change its state of motion.

How is net force related to velocity?

Net force is directly proportional to an object's acceleration, which is the rate of change of its velocity. The greater the net force acting on an object, the greater its acceleration and therefore, the greater its change in velocity.

What happens to an object's velocity when there is no net force acting on it?

If there is no net force acting on an object, its velocity will remain constant. This is known as the law of inertia, which states that an object will stay at rest or in motion with constant velocity unless acted upon by an external force.

Can an object have a net force of zero but still be moving?

Yes, an object can have a net force of zero and still be moving at a constant velocity. This is possible when the forces acting on the object are balanced, meaning they cancel each other out and do not result in a change in the object's motion.

How does the direction of net force affect an object's motion?

The direction of net force determines the direction of an object's acceleration. If the net force and the object's initial velocity are in the same direction, the object will speed up. If they are in opposite directions, the object will slow down. If the net force is perpendicular to the object's initial velocity, it will change the direction of the object's motion.

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