Part 2: Force
2.4.21 Newton's Laws of Motion
Lesson Overview
Newton’s Laws of motion are three physical laws that, together, laid the foundation for classical mechanics. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. They have been expressed in several different ways, and can be summarised as follows: First Law: An object in motion or at rest will move at the same constant velocity, unless acted upon by a force. Second Law: The net force on an object is equal to the mass of that object multiplied by the acceleration of the object. F = ma Third Law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. Textbook Pages:
- Review of forces from year 11 on page 154 - Newtons Laws on page 157 |
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2.4.22 Free Body Diagrams and Accelerated Motion
2.4.23 Vector Forces
Lesson Overview
When forces are applied to an object at different angles, the net resultant force can be found by breaking each force into it's x and y components and then adding parallel or opposing forces. Textbook pages 160-161
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2.4.24 TORQUE
Lesson Overview
Torque is a turning force. Its size depends on the magnitude of the applied force and the distance the force is applied from the pivot point, or fulcrum. Because torque is the product of a Force and a Distance, it is reported in Newton Meters (Nm). Note: This should not be confused with energy, which has the same base units. Textbook Pages: 169-170
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2.4.25 Torque and Equilibrium
Lesson Overview
When a system in in equilibrium, it means there is zero net force and therefore no acceleration. For equilibrium problems that involve torque, the net torque around any pivot force will also be zero. Clockwise Torque = Anticlockwise Torque Force up = Force down Force left = Force right Textbook Pages: 171-172
More Torque ActivitiesTorque Practical Investigation: Pages 173-177
More Practice Problems: 178-181 Double Pivot Points: 182-185 Angled Support Forces: 186-187 |
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2.4.26 CIRCULAR MOTION AND CENTRIPETAL ACCELERATION
Lesson Overview
Circular Motion is a movement of an object along the circumference of a circle or rotation along a circular path. Uniform Circular Motion (UCM) means that the speed of the object and the radius of the circle remain constant and the object is therefore rotating around a fixed axis. Examples of uniform circular motion include: a satellite orbiting a planet at constant height, a ball tied to a string and swung in horizontal circles, and a car turning through a curve. Because the object is constantly changing direction, the velocity vector is constantly changing direction, which is the result of acceleration by a centripetal force in the direction of the center of the circle. Without the centripetal force, there would be no acceleration, and the object would continue in a straight line according to Newton’s First Law of motion. Useful Formula Circumference of a circle: c = 2𝛑r Instantaneous speed: v = c/T = 2𝛑r/T Centripetal acceleration: ac = v^2/r Textbook Pages: 162-164
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2.4.27 Centripetal Force
Lesson Overview
The Centripetal Force is responsible for the centripetal acceleration in uniform circular motion. It can be calculated using: Centripetal Force: Fc = mac = mv^2/r Textbook Pages: 165-168
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