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Motion

Motion. Chapter 11. Motion. Motion is changing position against a fixed point. You can tell if something is moving if its position changes against some background that stays the same ( frame of reference ). Displacement is the change in position of an object. Motion.

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Motion

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  1. Motion Chapter 11

  2. Motion • Motion is changing position against a fixed point. • You can tell if something is moving if its position changes against some background that stays the same (frame of reference). • Displacement is the change in position of an object.

  3. Motion • Speed describes how fast an object moves (scalar). • Velocity describes the speed of an object plus the direction in which it is moving (vector). • Example: Tina the Llama escaped at a speed of 4.5 m/s. Tina the Llama escaped at a velocity of 4.5 m/s to the north.

  4. Motion Calculating speed and velocity: v = d / t velocity or speed distance time

  5. Motion • The cheetah, the fastest of land animals, can run a distance of 274 m in 8.65 s at its top speed. What is the cheetah’s top speed? v = d= t = ? v = d / t 274 m v = 274 m / 8.65 s 8.65 s V = 31.7 m/s

  6. Motion • Suppose the polar bear were running on land instead of swimming. If the polar bear runs at a speed of about 29,880 m/h, how far will it travel in 10.0 hours? v = d= t = 29,880 m/h t * v = d / t * t ? d = v * t 10 h d = 29,880 m/h * 10 h d = 298,800 m

  7. v v Motion • The various types of tree sloths share the honor of being the slowest-moving mammals. An average tree sloth moves with a speed of 0.743 m/s. How long does it take a sloth moving at this speed to travel 22.30 m? v = d= t = 0.743 m/s t * v = d / t * t 22.30 m v * t = d ? t = d / v t = 22.30 m / 0.743 m/s t = 30.0 s

  8. d v * t Motion • The various types of tree sloths share the honor of being the slowest-moving mammals. An average tree sloth moves with a speed of 0.743 m/s. How long does it take a sloth moving at this speed to travel 22.30 m? v = d= t = 0.743 m/s t = d / v t = 22.30 m / 0.743 m/s 22.30 m t = 30.0 s ?

  9. Motion • Speed can be shown on a distance-time graph. The slope of the line on this graph will be equal to the speed.

  10. Acceleration • Acceleration is any change in velocity (vector).

  11. Acceleration Calculating acceleration: a = v / t acceleration change in velocity time v = vf - vo

  12. Acceleration • Acceleration can be shown on a velocity-time graph. The slope of the line on this graph will be equal to the acceleration.

  13. Δv a * t Acceleration • A bicyclist accelerates at 0.89 m/s2 during a 5.0 s interval. What is the change in the speed of the bicyclist and the bicycle? a = Δv= t = 0.89 m/s2 Δv = a * t Δv = 0.89 m/s2 * 5.0 s ? Δv = 4.5 m/s 5.0 s

  14. Δv a * t Acceleration • An automobile accelerates 1.77 m/s2 over 6.00 s to reach freeway speed at the end of an entrance ramp. If the car’s final speed is 24.44 m/s, what was its initial speed when it began accelerating? a = Δv= t = 1.77 m/s2 Δv = a * t Δv = 1.77 m/s2 * 6 s ? Δv = 10.62 m/s 6 s Δv = vf - vo 10.62 = 24.44 - vo vo = 24.44 m/s – 10.62 m/s vo = 13.8 m/s

  15. Δv a * t Acceleration • The gravitational force between Mars and an object near its surface is much lower than the force between an object on Earth’s surface and Earth. If a dropped hammer’s speed increases from 0.0 m/s to 15.0 m/s in 4.04 s, what is the acceleration due to the gravitational force on the surface of Mars? a = Δv= = = t = ? a = v / t a = 15 m/s/ 4.04 s vf – vo a = 3.713 m/s2 15.0 m/s – 0.0 m/s 15.0 m/s 4.04 s

  16. Forces • A force is a push or pull. • This push or pull causes an object to change its velocity or acceleration.

  17. Forces • The combination of all the forces acting on an object is the net force. • This combination will determine whether the velocity of the object will change. • An object accelerates in the direction of the net force. • An object won’t accelerate if the net force is zero.

  18. Forces • Balanced Forces are equal in strength and cancel each other out. Motion does not change. The net force is zero. • Unbalanced Forces are not equal in strength and cause an object to change its velocity or acceleration. The net force is greater than zero.

  19. Forces

  20. Friction • Frictionis an unbalanced force that opposes motion. Friction resists the movement of one surface past another.

  21. Friction • There are three types of frictions: • Sliding Friction: Occurs when a solid surface slides over another solid surface. • Rolling Friction: Occurs when an object rolls across a solid surface. • Static Friction: Occurs between two objects that touch but do not move.

  22. Friction • Air Resistance is another type of friction. It occurs between the surface of a moving object and the air molecules.

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