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Holt Science Spectrum 21 Motion

Speedy Dinosaurs?Read the following paragraphs, and complete the exercises below.

Outside of a movie, or a bad dream, people are not likely to find themselves beingchased by a roaring Tryrannosaurus rex. But if they were, could they outrun thefierce beast? Scientists have uncovered indirect evidence to answer questionssuch as this one.

CLUES TO SPEED

Scientists use a number of clues to estimate how fast dinosaurs could run. One ofthese clues is called a trackway. A trackway is a sequence of fossilized footprintsmade by any animal. By analyzing the size of the feet and the distance betweensuccessive prints, scientists can get an idea of how fast the animal was movingwhen it made the prints. Using this method, scientists estimated a top speed ofabout 12 meters per second, or almost 27 miles an hour. How fast can a humanrun? The world record for 100 meters is 9.79 seconds.

Scientists also look for clues by comparing dinosaur skeletons those of existinganimals. Dinosaur skeletons are similar to those of present day mammals and birds,some of which are fast runners. Does this mean that dinosaurs were fast runners?Maybe. Maybe not. Scientists point out that large dinosaurs were built somethinglike elephants, which are not particularly fast runners. What about small dinosaurs?It’s highly possible they could speed across the ground at a good clip.

Exercises1. Based on data in the paragraphs, could a human outrun the fastest dinosaur?

2. Does a trackway necessarily show the maximum speed of a dinosaur?

3. In general, how is the size of a land animal related to the speed it can attain?

Name Class Date

Cross DisciplinarySkills Worksheet INTEGRATING BIOLOGY

Holt Science Spectrum 19 Motion

Friction in FictionRead the following paragraphs, and complete the exercises below.

Scientific terms are often used in a nonscientific context such as in a novel, shortstory, play, poetry, or in ordinary conversation. This is true of the term friction,which in science means an opposition to motion. Friction is caused when two sur-faces rub against each other. In a broader sense, friction means a state of disagree-ment or disharmony. Friction disagrees with, or is not in harmony with, motion.

This definition makes the term “conflict” a synonym for friction. A synonym is aword that has the same meaning, or nearly the same meaning, as one or moreother words. For example, the words fast, swift, speedy, quick, and rapid are allsynonyms of each other. War is a conflict that expresses a disharmony betweennations or groups. A debate between two candidates for a political office presentsa conflict, or disagreement, of ideas.

Exercises1. Use the term “friction” in a sentence describing an event in a fictional per-

son’s life.

2. Write a four-line poem, rhyming or not, in which the term “friction” appears.

3. Write a short fictional newspaper story. Use the term “friction” at least twice.Remember a newspaper story must answer the questions: who? what? where?when? why? Use a separate sheet of paper if needed.

Name Class Date

Cross DisciplinarySkills Worksheet CONNECTION TO LANGUAGE ARTS

Holt Science Spectrum 25 Motion

Designing Race CarsRead the following paragraphs, and complete the exercises below.

How is a car race won? Part of the answer is in the skill of the race driver and theskill and efficiency of the car’s pit crew. The design of the race car is also animportant factor.

OVERCOMING FRICTION

Friction is a backward force that opposes forward motion. Friction is causedwhen two surfaces rub against each other. Any medium—solid, liquid, or gas—produces friction on an object that moves through the medium. For example, arace car moving through air is affected by friction. This friction pushes the carbackward.

Friction varies directly with the roughness of one or both surfaces. Thus, thesmoothness of the surface is one factor that determines the amount of friction,and thereby affects the outcome of a race. All things being equal, a race car thatproduces the least amount of friction with air will win a race.

STREAMLINING

Shape is another factor that affects friction. What do sharks, airplanes, and racecars have in common? They all have streamlined shapes—somewhat pointed infront with gently curved surfaces that lead to their back ends. Streamliningreduces the resistance of a medium to the forward movement of an object—ashark through water, or an airplane or race car through air.

Exercises1. What are two factors that affect the amount of friction between a race car and

the air it moves through?

2. All things being equal, which will move more easily: a newly polished car or acar that’s never been polished? Explain.

3. All things being equal, which will move faster: a race car shaped like a box ora race car shaped like a rocket? Explain.

Name Class Date

Cross DisciplinarySkills Worksheet REAL WORLD APPLICATIONS

Holt Science Spectrum 18 Motion

The Motions of Dance Read the following paragraphs, and complete the exercises below.

A ballet performance is breathtaking. At one moment a dancer may leap throughthe air like a gazelle, seemingly defying gravity. A moment later, the dancer mayspin like a top. Still later, she might stand totally still on the tip of a single toe. Ineach case, the dancer is obeying —or taking advantage of — the laws of physics.

BALANCE

Whether in motion or at rest, dancers are experts in maintaining their balance.No feat of balance is more awesome than that of a ballerina standing absolutelystill on about one square inch of the toe of her slipper. A number of physical prin-ciples influence the balance of a dancer. One principle is Newton’s first law ofmotion: an object maintains its state of motion or rest unless it experiences anunbalanced force. For the ballarina to remain balanced, the sum of the forces act-ing on the ballerina, must be zero. For example, for the dancer to not moveupward or downward, the force of gravity — the dancer’s weight —must beequaled by an upward force exerted on the dancer by the floor.

CENTER OF GRAVITY

In addition, the center of gravity of the dancer must be at a point on a verticalline passing through the dancer’s body and through the tip of her toe at the floor.At that point, forces pushing the dancer in various directions cancel one another.The added force of a step, leap, or spin will set the dancer in motion again.

Exercises1. According to Newton’s first law, what will happen to an object that experi-

ences an unbalanced force?

2. How is the motion of a dancer related to the balance of forces acting on thedancer’s body?

3. Why is it easier to stand on a flat foot than on a single toe? Explain yourreasoning.

Name Class Date

Cross DisciplinarySkills Worksheet CONNECTION TO FINE ARTS

Holt Science Spectrum 26 Motion

Hiking in YellowstoneRead the following paragraphs, and then use Naismith’s rule and the map pro-vided to complete the exercises below. (Naismith’s rule: Allow 1 hour for every 3 mi traveled, then add 1 hour for every 2000 ft climbed.)

A group of outdoor enthusiasts was enjoying nature during a visit to YellowstoneNational Park. One morning, the group assembled for a hike at the beginning ofthe Beaver Ponds Loop Trail. When the group reached the Sepulcher Mountaintrail junction, half the hikers decided to complete the 2.5 mi hike and climb 350 ftto Beaver Ponds.

The other half of the group decided to veer off onto the Sepulcher MountainTrail. Starting at an elevation of 6252 ft, these hikers traveled a total of 5.5 mi toreach the summit of Sepulcher Mountain at 9652 ft.

Name Class Date

Cross-DisciplinarySkills Worksheet REAL WORLD APPLICATIONS

SepulcherMtn. Trail

Beaver PondsLoop Trail

BunsenPeak Trail

BunsenPeak

SepulcherMtn.

Beaver Ponds

2 MILES

GlenCreek

Gardner

River

X

X

LEGEND