I can not calculate the displacement

[maro_toni]

Hello,
Please help me solving this.


Q1-If you move 10 km North, 10 km East, and 10 km South,

a. What is your displacement? [ can not calculate it ]

b.What is the total distance you traveled? [30 km ]


2. The below graph represents the position of a mouse at a given time.
http://library.thinkquest.org/10796/ch2/Img00007.gif"

a. What is the average velocity between t = 0 to t = 4? [10 m/s]

b. What is the distance you traveled from t = 3 to t = 7? [ can not calculate it ]

c. What is the total displacement? [ can not calculate it ]

3. Answer the questions using the following graph.
http://library.thinkquest.org/10796/ch2/Img00008.gif"

a. What is the distance it traveled between t = 0 to t = 2? [20]

b. What is the instantaneous velocity when t = 4? [ can not calculate it ]

4. Jack and Michael are both running together at constant velocity of 10 m/s.

a. What is Jack's relative velocity to Michael? [10 i think ... but it's wrong]
b. What is Michael's relative velocity to Jack?


5. A rat and a cat are 25 m apart. When the rat started to run at 2 km/h, the cat started to chase him at 10 km/h. Can the cat catch the rat in 10 seconds?
YES??

so please help me to know who to calculate the [displacement-distance-relative velocity-instantaneous velocity]

i think each have a role (( equation )) but I cann't find them...
Please help..

Thank You. =)

 

[fss]

Q1-If you move 10 km North, 10 km East, and 10 km South,

a. What is your displacement? [ can not calculate it ]

Draw a picture and it should be obvious.

2. The below graph represents the position of a mouse at a given time.
http://library.thinkquest.org/10796/ch2/Img00007.gif"

a. What is the average velocity between t = 0 to t = 4? [10 m/s]

Correct. (Sorry, previously I had said this was incorrect.)

b. What is the distance you traveled from t = 3 to t = 7? [ can not calculate it ]

c. What is the total displacement? [ can not calculate it ]

What's the relationship between displacement and velocity? Once you answer this fundamental question this is a very easy problem.

3. Answer the questions using the following graph.
http://library.thinkquest.org/10796/ch2/Img00008.gif"

a. What is the distance it traveled between t = 0 to t = 2? [20]

The method you used to do this problem is the same you'd use for (b) and (c) in the previous problem.

b. What is the instantaneous velocity when t = 4? [ can not calculate it ]

Just look at the graph??

4. Jack and Michael are both running together at constant velocity of 10 m/s.

a. What is Jack's relative velocity to Michael? [10 i think ... but it's wrong]

10 m/s is incorrect. Re-read the question.

5. A rat and a cat are 25 m apart. When the rat started to run at 2 km/h, the cat started to chase him at 10 km/h. Can the cat catch the rat in 10 seconds?
YES??

How do you know? Figure out how far the rat and cat travel in 10 seconds at their respective velocities. Mind your units.

 

[zgozvrm]

a. What is the average velocity between t = 0 to t = 4? [10 m/s]

Incorrect.

Really? Why? Average velocity is defined to be the total distance traveled divided by the time it took to cover that distance. At time t=0, the mouse had traveled 0 m. At time t=4, the mouse had covered 40 m. So,

V_{avg} = \frac{(40 - 0)m}{(4-0)s} = 10 m/s

 

[zgozvrm]

4. Jack and Michael are both running together at constant velocity of 10 m/s.

a. What is Jack's relative velocity to Michael? [10 i think ... but it's wrong]
b. What is Michael's relative velocity to Jack?

Think of Jack and Michael both sitting in the same car, which is traveling at 10m/s. From Jack's perspective (compared to Jack), how fast is Michael moving?

 

[zgozvrm]

5. A rat and a cat are 25 m apart. When the rat started to run at 2 km/h, the cat started to chase him at 10 km/h. Can the cat catch the rat in 10 seconds?

I'm sure the intent of this question is to say that when the rat started running, it headed directly away from the cat (not towards, or at some other angle).
It is also assumed that there is no acceleration; the rat instantly is moving at 2 km/h and the cat is instantly moving at 10 km/h.


Also, note that we are dealing with several units here:

The distance between the rat and cat is given in meters.
Theirs speeds are given in kilometers per hour.
The time is given in seconds.

You should not only be able to determine if the cat can reach the cat in 10 sec, but exactly how long it would it would take for the cat to reach the rat, as well as how far each traveled before the cat had dinner.

 

[fss]

Really? Why? Average velocity is defined to be the total distance traveled divided by the time it took to cover that distance. At time t=0, the mouse had traveled 0 m. At time t=4, the mouse had covered 40 m. So,

V_{avg} = \frac{(40 - 0)m}{(4-0)s} = 10 m/s

Oops, I misread that one. You are correct, thanks for pointing that out.

 

[zgozvrm]

Oops, I misread that one. You are correct, thanks for pointing that out.

(Hey, it happens to all of us sometime!)

No problem ... you actually had me thinking that I didn't know what I was doing!