1. Motion Chapter 11

2. Motion Motion is changing position against a fixed point. 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). 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. Displacement is the change in position of an object.

3. Motion Speed describes how fast an object moves (scalar). Speed describes how fast an object moves (scalar). Velocity describes the speed of an object plus the direction in which it is moving (vector). 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. 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 distancetime

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? 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 = 274 m 8.65 s ?v = d / t v = 274 m / 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? 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 = ? 10 h 29,880 m/hv = d / t* tt * d = v * t d = 29,880 m/h * 10 h d = 298,800 m

7. 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? 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 = 22.30 m ? 0.743 m/sv = d / t* tt * v * t = d t = 22.30 m / 0.743 m/s t = 30.0 s t = d / v vv

8. 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? 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 = 22.30 m ? 0.743 m/s t = 22.30 m / 0.743 m/s t = 30.0 s t = d / v d v * t

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 accelerationchange in velocity time  v = v f - v o

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. Acceleration A bicyclist accelerates at 0.89 m/s 2 during a 5.0 s interval. What is the change in the speed of the bicyclist and the bicycle? A bicyclist accelerates at 0.89 m/s 2 during a 5.0 s interval. What is the change in the speed of the bicyclist and the bicycle? a = Δv= t = ? 5.0 s 0.89 m/s 2 Δv = 0.89 m/s 2 * 5.0 s Δv = 4.5 m/s Δv = a * t ΔvΔv a * t

14. Acceleration An automobile accelerates 1.77 m/s 2 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? An automobile accelerates 1.77 m/s 2 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 = ? 6 s 1.77 m/s 2 Δv = 1.77 m/s 2 * 6 s Δv = 10.62 m/s Δv = a * t ΔvΔv a * t Δv = v f - v o 10.62 = 24.44 - v o v o = 24.44 m/s – 10.62 m/s v o = 13.8 m/s

15. 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? 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 = v f – v o 4.04 s ? a = 15 m/s / 4.04 s a = 3.713 m/s 2 a =  v / t ΔvΔv a * t 15.0 m/s – 0.0 m/s 15.0 m/s