Acceleration and for direction

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    Acceleration Direction
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Discussion Overview

The discussion revolves around the calculation of acceleration and work done on an object being moved horizontally by a force applied at an angle. Participants explore the relationship between force components and the direction of motion, focusing on mechanical engineering concepts.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant questions whether to use the force acting at an angle or the resultant horizontal force to calculate acceleration.
  • Another participant clarifies that the horizontal component of the force should be used for calculating acceleration since the motion is purely horizontal.
  • A third participant emphasizes that the net force determines acceleration and that it has no vertical component in this scenario.
  • Further clarification is sought regarding the calculation of work done, specifically whether to use the horizontal force derived from trigonometric calculations or the total force connecting the crate and motor.
  • Participants confirm that the horizontal component of the force should be used to calculate work done, aligning with the direction of displacement.
  • One participant introduces the concept of the scalar product (dot product) in the context of work done.

Areas of Agreement / Disagreement

Participants generally agree on the need to use the horizontal component of the force for both acceleration and work done calculations. However, the discussion includes varying levels of detail and clarification regarding the definitions and calculations involved.

Contextual Notes

Some participants clarify terminology, such as the distinction between "resultant" and "resolved" forces. There is also an assumption that the object moves only horizontally, which may limit the applicability of the discussion to similar scenarios.

Who May Find This Useful

Students and individuals studying mechanical engineering or physics, particularly those interested in force analysis and motion in horizontal planes.

junkie_ball
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Hi,

I've just started studying a mechanical engineering course and have a real newbie question. If i have a force acting on a object at an angle to it above the horizontal that will be providing the velocity but the object will be moving along the horizontal to work out the acceleration will i need to calculate it using the force acting on it at the angle or the resultant horizontal force?

I hope that make sense?
 
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welcome to pf!

hi junkie_ball! welcome to pf! :wink:
junkie_ball said:
If i have a force acting on a object at an angle to it above the horizontal that will be providing the velocity but the object will be moving along the horizontal to work out the acceleration will i need to calculate it using the force acting on it at the angle or the resultant horizontal force?

you use the horizontal component (not "resultant" … a resultant is the force that results from adding two or more forces :wink: … though you can say "resolved") of the force

the reason is that everything has to be in the same direction …

the velocity (and the acceleration) is purely horizontal, so you resolve everything into horizontal components :smile:
 
What determines the acceleration is the net force on the object. If the object only moves horizontally, you know that the net force has no vertical component. So all you need worry about is the horizontal component of the force.
 
Thanks for the replies. So if i get this correctly i need to work the acceleration out on the horizontal. I have attached a diagram of the question. I'm not looking for an overall answer but clarification of my thinking.

In the attached the crate will be accelerated using a dragline at an angle but only move along the rollers horizontally. As such i will need to calculate the acceleration using the horizontal force which i can work out with trig. Is that correct?
 

Attachments

hi junkie_ball! :wink:
junkie_ball said:
In the attached the crate will be accelerated using a dragline at an angle but only move along the rollers horizontally.

As such i will need to calculate the acceleration using the horizontal force which i can work out with trig. Is that correct?

yes, that's correct :smile:

(and yes, the horizontal component is the force times cos of the angle between)
 
tiny-tim said:
hi junkie_ball! :wink:


yes, that's correct :smile:

(and yes, the horizontal component is the force times cos of the angle between)

Thanks for the confirmation! :approve:
 
Hi thanks for all you previous replies most helpful in my understanding. I now have one further query on the problem i attached in my previous post. To calculate work done i understand the equation is:

Work Done = Force x Displacement

As my displacement is in the horizontal plane does this mean i calculate the WD by using the horizontal force which i have worked out using trig or do i need to use the 50N force connecting the crate and motor? I'm assuming it's the horizontal force?
 
junkie_ball said:
I'm assuming it's the horizontal force?
Yes, you need to use the component of force in the direction of the displacement, in this case horizontal.
 
if you understand the scalar product (dot product), it's actually

Work Done = Force "dot" Displacement :wink:​
 

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