question

A track is made from a piece of channel iron as shown. A ball released at the left end of the track continues past the various points. Rank the speeds of the ball at points A, B, C, and D, from fastest to slowest.

answer

C (B & D at same score) A

question

Three balls of different masses are thrown straight upward with initial speeds as indicated. From fastest to slowest, rank the speeds of the balls 1s after being thrown. From greatest to least, rank the accelerations of the balls 1s after being thrown- or are the accelerations the same?

answer

a) BAC b) The acceleration will be the same because it will decelerate at 10 m/s squared.

question

Here we see top views of three motor boats crossing a river. All have the same speed relative to the water, and all experience the same river flow. Construct resultant vectors showing the speed and direction of each boat. Rank the boats from most to least for a) the time to reach the opposite shore b) the fastest ride. (I will send picture). We have absolutely no clue how to do this.

answer

B would arrive first because it has a more direct path as well as a shorter resultant.

question

Jo, with a reaction time of 0.2 seconds, rides her bike at a speed of 6.0 m/s. She encounters an emergency situation and immediately applies her brakes. How far does Jo travel before she actually applies the brakes?

answer

1.2m

question

Suzie Surefoot can paddle a canoe in still water at 8 km/h. How successful will she be canoeing upstream in a river that flows 8 km/h?

answer

She will not be very successful because she will be traveling at 0 km/h.

question

One airplane travels due north at 300km/h while another travels due south at 300 km/h. Are their speeds the same? Are their velocities the same?

answer

Speeds are the same because they are both going 300 km/h. Their velocities are the different because one plane is going due north while the other plane is going due south.

question

You're traveling in a car at some specified speed limit. You see a car moving at the same speed coming toward you. How fast is the car approaching you, compared with the speed limit?

answer

The car is approaching you at double the speed limit because the speed of your car and the speed of the other car are added together.

question

Jacob says acceleration is how fast you go. Emily says acceleration is how fast you get fast. They look to you for confirmation. Who is correct?

answer

Emily is correct because speed is how fast you go, and acceleration is a change in velocity.

question

What is the acceleration of a car that moves at a steady velocity of 100 km/h for 100s?

answer

Acceleration is 0 because the car is going at a steady velocity.

question

Galileo experimented with balls rolling on inclined planes for various angles. What is the range of accelerations from angles 0 degrees to 90 degrees? From what acceleration to what? I didn't know how to do this one.

answer

0 m/s squared-10 m/s squared

question

Suppose that a freely falling object in the preceding exercise were also equipped with an odometer. Would the readings of distance fallen each second indicate equal or different falling distances for successive seconds?

answer

There would be different readings because the acceleration is increasing, and that means the distance is getting greater between seconds.

question

If air resistance can be ignored, how does the acceleration of a ball that has been tossed straight upward compare with its acceleration if simply dropped?

answer

If a ball is tossed upward it slowly decelerates until it reaches equilibrium and changes direction. If a ball is dropped it accelerates until it hits the floor.

question

Boy Bob stands at the edge of a cliff and throws a ball nearly straight up at a certain speed and another ball nearly straight down with the same initial speed. If air resistance is negligible, which ball will have the greater speed when it hits the ground below?

answer

They are equal because they are thrown at the same initial speed, and their acceleration will be the same due to gravity.

question

While rolling balls down an inclined plane. Galileo observes that the ball rolls 1 cubit as he counts to 10. How far will the ball have rolled from its starting point when he has counted to 20?

answer

3 cubits

question

As speed increases for an object in free fall, does acceleration increase also?

answer

Acceleration will not change, it will remain at 10 m/s squared due to gravity.

question

Why would a person's hang time be considerably greater on the Moon than on Earth?

answer

There's much less gravity on the moon.

question

Vertically falling rain makes slanted streaks on the side of windows of a moving automobile. If the streaks make an angle of 45 degrees, how does the speed of the automobile compare with the speed of the falling rain?

answer

The automobile is going faster compared to the rain.

question

Make up a multiple choice question that would check a classmate's understanding of the distinction between velocity and acceleration.

answer

...

question

Can an object reverse its direction of travel while maintaining a constant acceleration? If so, cite an example to your classmates. If not, provide an explanation.

answer

No, because you will have to decelerate to change direction.

question

Correct your friend who says, "The dragster rounded the curve at a constant velocity of 100 km/h!"

answer

It went at a constant speed of 100 km/h, it did not go at a constant velocity because the direction is changing.

question

Cite an instance when your speed could be zero while your acceleration is a nonzero.

answer

Throwing a ball upwards and it reaching 0 at the top of it's path but it's acceleration is still 10 m/ sec squared.

question

a) Can an object be moving when its acceleration is zero? If so, give an example. B) Can an object be accelerating when its speed is zero? If so, give an example.

answer

a) Yes. If a car is moving at a constant velocity, it's acceleration will be zero. b)Throwing a ball upwards and it reaching 0 at the top of it's path but it's acceleration is still 10 m/ sec squared.

question

On which of these hills does the ball roll down with increasing speed and decreasing acceleration along the path?

answer

A. Because it will increase in speed, but it will eventually have a constant velocity.

question

Be picky and correct your friend who says, "in free fall, air resistance is more effective in slowing a feather than a coin."

answer

The acceleration will be equal because of gravity.

question

In the preceding exercise can you think of a reason why the acceleration of the object thrown downward through the air might be appreciably less than 10 m/s squared?

answer

Gravity accelerates at 10 m/s squared in a vacuum with no air resistance, so objects encountering air resistance actually don't accelerate at 10 m/s squared.

question

Madison tosses a ball straight upward. Anthony drops a ball. Your discussion partner says that both balls undergo the same acceleration. What is your response?

answer

I agree, but the acceleration will be in opposite directions. One will be accelerating and one will be decelerating.

question

Refer to the pair of tracks in the preceding exercise. A) On which track is the average speed greater? B) Why are the speeds of the balls at the ends of the track the same?

answer

a) A because the track is a constant straight line, and in B the track dips and has to go back up causing the ball to decrease in speed. B) They're released at the same time and the tracks are the same length (going the same distance), as well as the same height.

question

If rain drops fall vertically at a speed of 3 m/s and you are running horizontally running at 4 m/s convince your classmates that the drops will hit your face at a speed of 5 m/s.

answer

use the pythagorean theorem and solve.

question

In this chapter, we studied idealized cases of balls rolling down smooth planes and objects falling with no resistance. Suppose a classmate complains that all this attention focused on idealized cases is worthless because idealized cases don't simply occur in everyday world. How would you respond to this complaint? How do you suppose the author of this book would respond?

answer

You have a valid point, but you must learn in ideal situations because you must understand the basics before you add in air resistance and friction.