Many students think that, if an object has a speed of zero (even instantaneously), it has no acceleration

• Acceleration and deceleration (11 - 14)

  Making clear the forces acting on an object - throwing a ball means the 'driving' force is only acting when the ball is in your hand and after that the forces are air resistance and gravity.  These will affect the velocity and the acceleration.

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References

• Twigger, D.; Byard, M.; Driver, R.; Draper, S.; Hartley, R.; Hennessy, S.; Mohamed, R.; O'Mally, C.; O'Shea, T. and Scanlon, E. (1994) The conception of force and motion of students aged between 10 and 15 years: an interview study designed to guide instruction. International Journal of Science Education, 16 (2), 215-229.

  Students can be very unclear about the difference between energy and force, often believing that they are the same thing. This leads then to the idea that objects slow down because they are ‘using up’ energy, rather than realising that forces are acting to change the motion. This study suggests that careful analysis of motion graphs, coupled with force diagrams can help overcome these issues and that the concept of momentum should be introduced earlier in many courses.
  
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