skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Thursday, October 10 until 2:00 AM ET on Friday, October 11 due to maintenance. We apologize for the inconvenience.

Explore Research Products in the NSF-PAR

Title: Impetus-Force-Like Drawings May Be Less Common Than You Think
Perhaps the most commonly cited student idea about forces in the literature is the notion of an impetus force, defined as the “belief that there is a force inside a moving object that keeps it going and causes it to have some speed,” that can then “fade away as the object moves along.” According to the literature, even after physics instruction students use impetus force reasoning to argue that forces are necessary to sustain motion or that motion implies force. For example, many students drew an upward arrow to indicate a force on a coin that was moving upward after being tossed. The coin was halfway between the point of its release and its turnaround point. Interviews with students in the course indicate that the arrow was meant to indicate “the ‘force of the throw,’ the ‘upward original force,’” and so on. Clement interprets these results to mean that students “believe that continuing motion implies the presence of a continuing force in the same direction, as a necessary cause of the motion.”  more » « less
Award ID(s):
1914603 1914572
NSF-PAR ID:
10357657
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
The Physics Teacher
Volume:
60
Issue:
4
ISSN:
0031-921X
Page Range / eLocation ID:
254 to 257
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ( , Journal of Geophysical Research: Atmospheres)
    Abstract

    A positive cloud‐to‐ground (+CG) lightning flash containing a single stroke with a peak current of approximately +310 kA followed by a long continuing current triggered seven upward lightning flashes from tall structures. The flashes were observed on 4 June 2016 at the Tall Object Lightning Observatory in Guangzhou, Guangdong Province, China. The optical and electric field characteristics of these flashes were analyzed using synchronized two‐station data from two high‐speed video cameras, one total‐sky lightning channel imager, two lightning channel imagers, and two sets of slow and fast electric field measuring systems. Three upward flashes were initiated sequentially in the field of view of high‐speed video cameras. One of them was initiated approximately 0.35 ms after the return stroke of +CG flash from the Canton Tower, the tallest structure within a 12‐km radius of the +CG flash, while the other two upward flashes were initiated from two other, more distant tall objects, approximately 18 ms after the +CG flash stroke. The initiation of the latter two upward flashes could be caused by the combined effect of the return stroke of +CG flash, its associated continuing current, and K process in the cloud. Each of these three upward flashes contained multiple downward leader/upward return stroke sequences, with the first leader/return stroke sequence of the second and third flashes occurring only after the completion of the last leader/return stroke sequence of the preceding flash. The total number of strokes in the three upward flashes was 13, and they occurred over approximately 1.5 s.

     
    more » « less
  2. ; ( , Infancy)

    Infants represent objects that are endpoints in motion events and show a preference for encoding the endpoint (the duck waddles into abowl) over the starting point (the duck waddles out of abox). This asymmetry continues to appear in nonlinguistic cognition and language throughout development. This study tests whether this asymmetry also shows up in 16‐month‐old infants’ visual preferences for motion events, and if so, for which types of events. Infants looked longer at events depicting an “agentive” figure (e.g., duck) moving into an object (endpoint) than out of an object (starting point), and this asymmetry persisted even when the starting point object was larger and more colorful than the endpoint object and when it caused the motion of the figure. However, an asymmetry was not found when motion into/out of the endpoint/starting point involved was performed by a “nonagentive” (e.g., leaf) figure. These findings suggest that an endpoint/starting point asymmetry in infant cognition (1) extends to infants’ visual preferences of motion events, (2) shows up most strongly for events that involve an “agentive” figure, and (3) is largely unaffected by the physical saliency of the starting point object. How a visual endpoint preference may support the acquisition of spatial language is considered.

     
    more » « less
  3. ; ( , Physical Review E)
    Acoustic traps use forces exerted by sound waves to confine and transport small objects. The dynamics of an object moving in the force landscape of an acoustic trap can be significantly influenced by the inertia of the surrounding fluid medium. These inertial effects can be observed by setting a trapped object in oscillation and tracking it as it relaxes back to mechanical equilibrium in its trap. Large deviations from Stokesian dynamics during this process can be explained quantitatively by accounting for boundary-layer effects in the fluid. The measured oscillations of a perturbed particle then can be used not only to calibrate the trap but also to characterize the particle. 
    more » « less
  4. ; ; ; ; ( , Journal of Research in STEM Education)
    Performance assessment (PA) has been increasingly advocated as a method for measuring students’ conceptual understanding of scientific phenomena. In this study, we describe preliminary findings of a simulation- based PA utilized to measure 8th grade students’ understanding of physical science concepts taught via an experimental problem-based curriculum, SLIDER (Science Learning Integrating Design Engineering and Robotics). In SLIDER, students use LEGO robotics to complete a series of investigations and engineering design challenges designed to deepen their understanding of key force and motion concepts (net force, acceleration, friction, balanced forces, and inertia). The simulation-based performance assessment consisted of 4 tasks in which students engaged with video simulations illustrating physical science concepts aligned to the SLIDER curriculum. The performance assessment was administered to a stratified sample of 8th grade students (N=24) in one school prior to and following implementation of the SLIDER curriculum. In addition to providing an illustration of the use of simulation- based performance assessment in the context of design-based implementation research (DBIR), the results of the study indicate preliminary evidence of student learning over the course of curriculum implementation. 
    more » « less
  5. ; ( , Scientific Reports)
    Abstract

    Dexterous manipulation relies on the ability to simultaneously attain two goals: controlling object position and orientation (pose) and preventing object slip. Although object manipulation has been extensively studied, most previous work has focused only on the control of digit forces for slip prevention. Therefore, it remains underexplored how humans coordinate digit forces to prevent object slip and control object pose simultaneously. We developed a dexterous manipulation task requiring subjects to grasp and lift a sensorized object using different grasp configurations while preventing it from tilting. We decomposed digit forces into manipulation and grasp forces for pose control and slip prevention, respectively. By separating biomechanically-obligatory from non-obligatory effects of grasp configuration, we found that subjects prioritized grasp stability over efficiency in grasp force control. Furthermore, grasp force was controlled in an anticipatory fashion at object lift onset, whereas manipulation force was modulated following acquisition of somatosensory and visual feedback of object’s dynamics throughout object lift. Mathematical modeling of feasible manipulation forces further confirmed that subjects could not accurately anticipate the required manipulation force prior to acquisition of sensory feedback. Our experimental approach and findings open new research avenues for investigating neural mechanisms underlying dexterous manipulation and biomedical applications.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email