• Medgirl314
In summary, the conversation revolved around solving two problems, one involving a dog's average speed and velocity, and the other involving the time it takes for two cars to pass each other on a straight road. The individual seeking help provided their attempted solutions and asked for confirmation. The expert pointed out a mistake in the calculation for the dog's velocity and provided the correct answer. The individual then corrected their mistake and thanked the expert for their help.
Medgirl314

## Homework Statement

I have two problems.

1. Your dog is sent to fetch the newspaper in the morning. He runs directly away from you,traveling 62.0 feet in 5.0 seconds. He then turns around and in 4.0 seconds runs 30 feet back toward you before deciding to stop. Calculate the dog's average speed and average velocity.

2. Two cars are traveling 12 miles apart and are approaching each other on a straight road. Each car is moving at 60 million/h relative to the road. How long will it take before the cars pass each other? Give your answer in minutes.

## The Attempt at a Solution

I am pretty sure of my answers, but would like to check them before turning them in.
1. Speed: 10 ft/s Velocity: 32 ft/s

2. 6 minutes.

Medgirl314 said:
1. Speed: 10 ft/s Velocity: 32 ft/s
The speed is about right (don't know how many significant figures are required), but for the velocity you appear to have forgotten to do something.
The time in q2 is right.

1 person
Thank you! Do you have an idea of what I may have forgotten? For the velocity I subtracted 30 ft. from 60 ft. and then divided by 5 seconds minus four seconds, yielding 32 ft. over 1 second, yielding my answer of 32 ft./s

Medgirl314 said:
Thank you! Do you have an idea of what I may have forgotten? For the velocity I subtracted 30 ft. from 60 ft. and then divided by 5 seconds minus four seconds, yielding 32 ft. over 1 second, yielding my answer of 32 ft./s
Why did you subtract 4 seconds from 5 seconds? Did time run backwards?

1 person
Oh! Thank you! I assumed that since I subtracted in the numerator I should subtract in the denominator, but I wasn't thinking critically. So I would actually add 4 and 5, yielding an average velocity of 3.5 ft/s.

Medgirl314 said:
Oh! Thank you! I assumed that since I subtracted in the numerator I should subtract in the denominator, but I wasn't thinking critically. So I would actually add 4 and 5, yielding an average velocity of 3.5 ft/s.
Much better.

Thank you! That was the one answer that seemed off.

Wow. I can't believe I misspelled "problems" in this. I should drink more coffee before attempting physics tomorrow.

## 1. How do I check the speed/velocity problem answers?

To check the speed/velocity problem answers, you can use the formula "speed = distance/time". This will give you the average speed.

## 2. What units should I use for speed/velocity?

Speed/velocity can be measured in various units such as meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), or feet per second (ft/s). It is important to use the units that are appropriate for the given problem.

## 3. How can I determine the direction of velocity?

Velocity has both magnitude (speed) and direction. The direction of velocity can be determined by using a compass or by using positive and negative signs. Positive velocity indicates movement in the forward or upward direction, while negative velocity indicates movement in the backward or downward direction.

## 4. What is the difference between speed and velocity?

Speed is the rate at which an object is moving, while velocity is the rate at which an object is moving in a specific direction. Speed does not take into account the direction of movement, while velocity does.

## 5. How do I calculate instantaneous speed/velocity?

Instantaneous speed/velocity is the speed/velocity of an object at a specific moment in time. To calculate it, you can use the formula "instantaneous speed/velocity = change in distance/change in time". This will give you the speed/velocity at a particular point in time.

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