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You can describe the motion of an object by what?
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Motion is everywhere. Easy to __________, hard to _________.
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ch4 physics
physics notes for ch.4
| Question | Answer |
|---|---|
| You can describe the motion of an object by what? | its position, speed, direction, and acceleration |
| Motion is everywhere. Easy to __________, hard to _________. | recognize, describe |
| Who helped explain motion by studying balls rolling on inclined planes? | Galileo |
| Who were confused about motion? | the Ancient Greeks |
| An object is moving if its ________ relative to a fixed point is ________. | position, changing |
| What means in respect to something else? | relative |
| A book is relative to a ____. | desk |
| The Earth is relative to the ___. | sun |
| Even things that appear to be at rest ____. | move |
| A book that is at rest, relative to the table it lies on, is moving at about ______ relative to the sun. | 30 km/s |
| The book moves even ______ relative to the center of our ______. | faster, galaxy |
| Although you may be at rest relative to Earth's surface, you're moving at about _________ relative to the ___. | 100,000 km/h, sun |
| Who was speed first calculated by? | Galileo |
| Speed is how ____ something is moving. | fast |
| Speed is a ____. | rate |
| Speed is distance per ____. | time |
| Units for speed could include any combination of units for ________ and ____. | distance, time |
| The fastest unit for speed is miles per hour. In symbols = | mi/h |
| The second fastest unit for speed is kilometers per hour. In symbols = | km/h |
| The second slowest unit for speed is centimeters per ___. | centimeters |
| The slowest unit for speed is light-years per _______. | century |
| We will primarily use the unit ______ per second (m/s) for speed. | meters |
| What's the fastest land animal over distances less than 500 meters and can achieve peak speeds of 100 km/h? | a cheetah |
| If a cheetah covers 50 meters in a time of 2 seconds, its speed is ____. | 25 m/s |
| In what two ways can speed be described as? | instantaneous and average |
| What is the speed at any moment in time? | instantaneous |
| Instantaneous speed is shown on the __________ of a car. | speedometer |
| What speed is the total distance covered divided by the total time? | average |
| Does the tortoise or the hare run at a faster speed? | the hare |
| Does the tortoise or the hare have the faster average speed? | the tortoise |
| KNOW WHY THE TORTOISE WON THE RACE IN TERMS OF INSTANTANEOUS AND AVERAGE SPEEDS | KNOW WHY THE TORTOISE WON THE RACE IN TERMS OF INSTANTANEOUS AND AVERAGE SPEEDS |
| Speed is a description of how fast an object moves; ________ is how fast and in what direction it moves. | velocity |
| What is speed in a given direction? | velocity |
| What are the two components of velocity? | speed and direction |
| Velocity is a ______ quantity because it gives direction as well as _________(speed). | vector, magnitude |
| 3 m/s north is an example of what? | velocity |
| ________ velocity means that both aspects of velocity must remain unchanged. | Constant |
| Constant velocity maintains the same _____, same _________, and continues in a straight line. | speed, direction |
| ________ velocity means that either or both aspects of velocity must be changing. | Changing |
| Changing velocity maintains different _____ and _________. | speed, direction |
| The car is driving in a circle and its speed is remaining at 25 km/h, is its velocity constant or changing and why? | It is changing velocity because its direction is changing. |
| On a car, there are 3 controls that can change ________. | velocity |
| What control increases speed? | the gas pedal |
| What control decreases speed? | the brake |
| What control changes direction? | the steering wheel |
| A car is traveling northward at 60 km/h. It passes another car traveling southward at 60 km/h. Do both cars have the same speed? Do they have the same velocity? | They have the same speed but they have opposite velocities because they are moving in different directions. |
| ____________ is the rate at which velocity changes. | Acceleration |
| For acceleration to occur, speed must ________ or ________, or direction must change. | increase, decrease |
| What is deceleration? | negative acceleration |
| To accelerate in the direction of velocity means to _______. | speed up |
| To accelerate against velocity means to ________. | slow down |
| To accelerate at an angle to velocity means to change _________. | direction |
| The unit for time appears _____: once for the unit of speed and again for the interval of time in which the speed is changing. | twice |
| A car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration? | The speed increases by 5 km/h each 1s interval in a straight line. |
| What is the acceleration of an object in free fall? | about 10 meters per second squared (10 m/s squared) |
| A falling object ___________ as it falls. | accelerates |
| What causes the acceleration of an object? | gravity |
| ________ is motion due only to the effect of gravity. | Free fall |
| What is the time that passes from the beginning of the free fall? | elapsed time |
| If one considers the speed of a falling rock, what develops? | a pattern |
| In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vehicle? | The car and the truck both increase their speed by 15 km/h during the same time interval, so their acceleration is the same. |
| If the elapsed time is 2, the instantaneous speed is __. If the elapsed time is 5, the instantaneous speed is __. | 20, 50 |
| During each second of fall the __________ speed of the object increases by an additional __ meters per second. | instantaneous, 10 |
| What is the gain in speed per second? | acceleration |
| The unit of speed occurs twice, once for _____ and once for the ____________. | speed, time interval |
| The instantaneous speed of an object falling from rest is equal to what? | the acceleration multiplied by the elapsed time |
| What is the average speed of any object moving in a straight line with constant acceleration? | the average of the initial speed and the final speed |
| The average speed of a freely falling object in its first second of fall is the ___ of the initial speed of zero and the final speed of 10 m/s, _______ by 2, or 5 m/s. | sum, divided |
| Average speed is _________ from instantaneous speed. | different |
| Objects thrown straight upward gradually ________ speed (upward) and stop at the top. | decrease |
| Objects thrown straight upward gradually ________ speed (downward). | increase |
| Any change in the object thrown straight upward is due to _______. | gravity |
| What would the speedometer reading on the falling rock be 4.5 seconds after it drops from rest? | 45 m/s |
| What would the speedometer reading on the falling rock be 8 seconds after it drops from rest? | 80 m/s |
| For each second of free fall, an object falls a _______ distance than it did in the previous second. | greater |
| At the end of the first second, the free-falling object has an instantaneous speed of what? | 10 m/s |
| What is the initial speed of an object in free fall in the first second? | 0 m/s |
| During the first second, the object has an average speed of 5 m/s, so it falls a distance of _________. | 5 meters |
| If a falling rock is equipped with an odometer, the readings of distance fallen ________ with time. | increase |
| For freely falling objects, what increases each second? | velocity |
| For freely falling objects, what remains at a constant rate, g? | acceleration |
| The distance a freely falling object falls each second _________. | increases |
| On what kind of graph does the slope represent speed per time, or acceleration? | speed-versus-time graph |
| True or false? Equations and tables are not the only way to describe relationships such as velocity and acceleration. | True |
| Graphs can visually describe _____________. | relationships |
| On a speed-versus-time graph, the speed(v) of a freely falling object can be plotted on the ________ axis and time(t) on the __________ axis. | vertical, horizontal |
| What does the "curve" that best fits the points form? | a straight line |
| For every increase of 1s on a speed-versus-time graph, there is the same 10 m/s increase in _____. Mathematicians call this _________. | speed, linearity |
| Since the object is dropped from rest, the line on a speed-versus-time graph starts at the origin, where both v and t are ____. | zero |
| If we double t, we ______ v; if we triple t, we ______ v; and so on. This particular linearity is called a direct proportion. | double, triple |
| Time and speed are directly ____________ to each other. | proportional |
| The curve on a speed-versus-time graph is a ________ line, so its slope is ________. | straight, constant |
| For 10 m/s of vertical change there is a horizontal change of __. | 1s |
| If the acceleration on a speed-versus-time graph were greater, the slope of the graph would be _______. | steeper |
| VIEW ALL CHARTS AND GRAPHS IN NOTES | VIEW ALL CHARTS AND GRAPHS IN NOTES |
| What is a decreasing acceleration or negative acceleration called? | deceleration |
| Constant speed is called ____ acceleration. | zero |
| When the distance(d) traveled by a freely falling object is plotted on the vertical axis and time(t) on the horizontal axis, the result is a ______ line. | curved |
| The distance-versus-time graph is _________. | parabolic |
| The relationship between distance and time is _________. | nonlinear (not straight) |
| The relationship between distance and time is _________ and the curve is parabolic - when we double t, we do not double d; we _________ it. | quadratic, quadruple |
| What does distance depend on? | time squared |
| How do you find the average speed(v)? | d/t |
| How do you find the acceleration(a)? | vf-vi/t |
| How do you find the instantaneous speed(v)? | gt |
| How do you find the distance(d)? | 1/2g t squared |
| A curved line also has a _____ - different at different points. | slope |
| The slope of the curve on a distance-versus-time graph is _____. | speed |
| The slope ________(becomes greater) as time passes, which shows that speed _________ as time passes. | steepens, increases |
| Air resistance noticeably _____ the motion of things with large surface areas like falling feathers or pieces of paper. But air resistance ____ noticeably affects the motion of more compact objects like stones and baseballs. | slows, less |
| If you drop a feather and a coin in air, the ____ hits the ground first because the ___ affects the feather more than the coin. | coin, air |
| The dropped feather has more _______ ____ than the coin. | surface area |
| If you drop a feather and a coin in a vacuum, they both hit at the ____ ____. | same time |
| What is the rate at which velocity changes? | acceleration |
| "How fast" and "how far" are completely _________. | different |
| How fast something freely falls from rest after a certain elapsed time is _____ or ________. | speed, velocity |
| How far the object has fallen is ________. | distance |
| How quickly speed (or velocity) changes is ____________. | acceleration |
| What makes acceleration so complex? | that it is a rate of a rate |
| Acceleration is often confused with ________, which itself is a rate (the rate at which distance is covered). | velocity |
| Acceleration is NOT ________, nor is it even a ______. | velocity, change |
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jessicamoore