Worksheet

1. ejss_model_kinematics CT_kinematics (1017).ppt 2017 by Dave
2. ejss_model_kinematics Motion in One Dimension student worksheet (2017).docx 2017 by Dave
3. Motion in One Dimension student worksheet (dl-gwf) Link1, Link2  by Lyna, Gavin, Dave and lookang 

Examples

From Dave and Gavin,

1.A sky diver jumps out of a hovering helicopter. A 2 seconds afterwards another sky diver jumps out and they both fall along the same vertical line. Ignore air resistance so that both sky divers fall with the same acceleration.
a.Does the difference in their speeds stay the same throughout the fall?

https://iwant2study.org/ospsgx/index.php/interactive-resources/physics/02-newtonian-mechanics/01-kinematics/37-kinematics-in-y-direction

suggested answer: after t =2 s, the difference is always the same difference as shown by the constant difference.

b.Does the vertical distance between them stay the same throughout the fall?

https://iwant2study.org/ospsgx/index.php/interactive-resources/physics/02-newtonian-mechanics/01-kinematics/37-kinematics-in-y-direction

suggested answer: after t =2 s, the difference in position increases as shown by the increasing difference of YELLOW minus BLUE line.


Question 2

2.A tennis ball thrown from the top of a building is given an initial velocity of 20 m/s straight upward. The building is 50 m high, and the ball just misses the edge of the roof on its way down. Using t = 0 as the time the ball leaves the thrower’s hand, determine
a.the time at which the ball reaches its maximum height

https://iwant2study.org/ospsgx/index.php/interactive-resources/physics/02-newtonian-mechanics/01-kinematics/37-kinematics-in-y-direction

suggested answer: t = 2.0 s 

b.the maximum height

suggested answer: H maximum = 70.4 m 

c.the time at which the ball returns to the height from which it was thrown

https://iwant2study.org/ospsgx/index.php/interactive-resources/physics/02-newtonian-mechanics/01-kinematics/37-kinematics-in-y-direction

suggested answer: t = 4.0 or 4.1 s 

d.the velocity of the ball at this instant


suggested answer: v = -20.2 m/s


e.the velocity and position of the ball at t = 5 s

https://iwant2study.org/ospsgx/index.php/interactive-resources/physics/02-newtonian-mechanics/01-kinematics/37-kinematics-in-y-direction

Key inquiry question:

How can we describe the motion of objects moving in a straight line?

1. Speed, velocity and acceleration

• Physical quantities can be scalar (e.g. distance, speed) or vector (e.g. displacement, velocity, acceleration) quantities. Scalar quantities can be added algebraically. Vector quantities can be added using graphical methods (parallelogram method or ‘head-to-tail’ method).

• Average speed of a body is given by total distance travelled / total time taken (v = d/t). Instantaneous speed is the speed at any instant.

• Acceleration of a body is defined as its change in velocity / time taken (a = (v - u)/t). The direction of acceleration is the direction of the change in velocity.

• Acceleration is: zero when velocity is constant (i.e. no change in velocity); positive (object is accelerating) when velocity is increasing; negative (object is decelerating) when velocity is decreasing

2. Graphical analysis of motion

• Displacement-time and velocity-time graphs of a body allow us to deduce when the body is: at rest; moving with uniform velocity and acceleration; moving with non-uniform velocity and acceleration.

• Gradient of a displacement-time graph gives the velocity of the moving object; Gradient of a velocitytime graph gives the acceleration of the moving object; Area under a velocity-time graph gives the displacement travelled by a body.

3. Free fall

• An object is in free fall if the only force acting on it is the force of gravity (it’s weight), i.e. no air resistance or contact forces act on the falling object.

• Acceleration of free fall, g for a body near to the Earth is constant and is approximately 10 m/s2 (regardless of the object’s mass or size).

4. Effect of air resistance

• The motion of bodies with constant weight falling with or without air resistance are different (without air resistance, object will have constant acceleration and velocity increases continuously; with air resistance, velocity reaches maximum value or terminal velocity when the force due to air resistance = weight, and acceleration becomes zero). Terminal velocity occurs only when air resistance is considered

Students’ prior knowledge of Kinematics

Primary level:

Students will not have been introduced to the concepts to describe motion. They would have knowledge of the effects of a force to stop or move an object; change its speed (move faster or slower) or direction of motion.

Lower secondary level:

Students learn that speed:

• is a measure of how fast an object is moving;

• depends on the distance (length) travelled and the time taken (unit: m/s).

Objects usually do not move at the same speed, hence, it is more useful to measure its average speed which is defined as total distance travelled / total time taken. Speed at any instant is the average speed over an extremely short time interval.

Students’ common misconceptions and learning difficulties in Kinematics

Displacement, velocity and acceleration:

1. Students’ concepts of displacement, velocity, and acceleration are not well differentiated.
2. They often think that: same position means same velocity for two objects; same velocity means same acceleration for two objects; larger (or smaller) velocity means larger (or smaller) acceleration; zero velocity means zero acceleration; and acceleration and velocity are always in the same direction.
3. Displacement-time and velocity-time graphs: Students often view the position and velocity graphs as the actual path of the object, rather than a graphical representation of an object’s motion
4. A hammer will reach the bottom (Moon’s surface) first as it is heavier than the feather since there is higher gravitational pull on the hammer, when in fact the hammer and feather have the same acceleration due to gravity and they will reach the ground at the same instance in an environment where there is no air resistance.
5. Some students treat gravitational force and weight as separate forces, when in fact Weight of an object is the gravitational force between the object and the Earth.
6. Students think that an external force is necessary to keep an object in motion when in fact An object does not need an external force to keep it moving at a constant speed in a straight path, if forces opposing motion such as friction is negligible.

 Computational Thinking

Versions

1. http://weelookang.blogspot.sg/2016/01/ejss-free-fall-simulation-added-more.html Blogpost on more cases added
2. http://weelookang.blogspot.sg/2014/03/ejss-kinematics-in-y-model.html Blogpost on JavaScript version by Loo Kang Wee 
3. http://weelookang.blogspot.sg/2013/12/ejss-free-fall-model.html Blogpost on JavaScript version by Loo Kang Wee
4. http://weelookang.blogspot.sg/2013/12/ejss-kinematics-model.html template objects from lookang
5. http://weelookang.blogspot.sg/2010/09/ejs-open-source-bouncing-ball-with-drag.html Blogpost on Java vesion by Loo Kang Wee and Fu-Kwun Hwang
6. http://weelookang.blogspot.sg/2010/06/ejs-open-source-kinematics-java-applet.html
7. http://www.compadre.org/osp/items/detail.cfm?ID=13050 Physlet One-Dimensional Kinematics Illustrations Package by Andreu Glasmann, Wolfgang Christian, and Mario Belloni

Other Resources

1. http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=421.0 Elastic bouncing ball Java Version by Fu-Kwun Hwang
2. http://butikov.faculty.ifmo.ru/Projects/Falling_bodies.html#_applet Falling Object Java 3D version by Eugene Butikov
   

Other Hands-on kit

1. https://sites.google.com/site/iprofmeca/session-1-free-fall by This email address is being protected from spambots. You need JavaScript enabled to view it.

Project related:

1. AEP 03/16 LW Apps as Virtual Lab
2. Understanding Teacher Learning Community as Support for Implementation of Open Source Physics for Conceptual Instruction Project Number: OER 10/15 GWF Project Duration: 01 July 2015 - 30 April 2017 http://weelookang.blogspot.sg/2015/07/understanding-teacher-learning.html

Family of Resources

end faq