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# 7-1 Forces

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### 7-1 Forces

1. 1. Warm-Up<br />Which encounters a greater force of air resistance? A feather or an elephant. Explain.<br />There is greater force of air on the elephant because its surface area is large. But the force of air on it is very small compared to its weight. <br />
2. 2. 7-1 - Forces<br />Describe examples of force and Identify appropriate SI units used to measure force.<br />Explain how motion of an object is affected when balanced and unbalanced forces act on object.<br />Compare and Contrast the four kinds of friction.<br />Describe how Earth’s gravity and air resistance affect falling objects.<br />
3. 3.
4. 4. Force<br />A push or a pull that causes a change in motion.<br />Measured inNewtonswith a spring scale.<br />1 kg accelerated at 1 m/s2 would require 1 N of force.<br />A small apple weighs about 1Newton.<br />
5. 5. Forces that affect motion<br />Fa- Applied Force <br />a force exerted on an object by other objects in it’s environment.<br />Ff - Frictional Force<br />a force that opposes motion between the object and the surface it rests upon.<br />Fg- Gravitational Force<br />the force of attraction between two objects with mass.<br /> (ex. Between an object and the Earth)<br />Fn - Normal Force <br />the supportive force of the surface an object rests upon. <br />Normal means “perpendicular”<br />Fnet –Net Force <br />Sum of all forces<br />
6. 6. Understanding Check-up<br />Are forces scalar or vectors?<br />Thumbs up – Scalar<br />Thumbs down – vector.<br />Does the direction of the push matter?<br />
7. 7. Combining forces acting on an object<br />
8. 8. Force Diagrams<br />Arrows drawn to represent the size and direction of force. <br />All arrows are drawn from center of object.<br />
9. 9. If forces are balanced…No Change Motion<br /><ul><li>No net (unbalance) forces.</li></ul>Fn<br />50N, up<br />Fg<br />Fn<br />Fg<br />50N, down<br />
10. 10. Direction of motion<br />If forces are unbalanced…Motion<br /><ul><li> Net (unbalanced) force.</li></ul>Net force<br />Fg<br />Fn<br />Fn<br />Fg<br />
11. 11. If forces are balanced…No Change in Motion<br />No net (unbalance) forces.<br />Ff<br />Fn<br />Ff<br />Fn<br />Fg<br />Fg<br />
12. 12. Friction<br />Friction force is a force that resists or opposes motion.<br />Friction force is present when other forces are present.<br />Types of Friction<br />Static Friction<br />Acts on objects that are not moving but other forces are trying to move the object . <br />Sliding Friction<br />Acts on object that is moving.<br />Rolling Friction<br />Acts on objects that roll.<br />Fluid Friction<br />Acts on objects that are in fluids.<br />A fluid is matter that can flow and has no shape.<br />
13. 13. Gravity<br />Gravity is an attractive force that acts between two masses.<br />Gravity acts towards the center of the earth or any other object.<br />Gravity’s affects are everywhere.<br />There is gravity in space. Its just very small.<br />
14. 14. Summary of Forces<br />What is a force?<br />A push or a pull that causes acceleration.<br />What are the four type of friction?<br />Static<br />Sliding<br />Rolling<br />Fluid<br />Where does gravity act?<br />Everywhere even in space<br />
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