- #1

- 6

- 0

a) the displacement vector in unit-vector notation

b) the average velocity vector in unit-vector notation

c) the average acceleration vector in unit-vector notation

d) calculate the magnitude and direction of the average acceleration vector

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter popmop2
- Start date

- #1

- 6

- 0

a) the displacement vector in unit-vector notation

b) the average velocity vector in unit-vector notation

c) the average acceleration vector in unit-vector notation

d) calculate the magnitude and direction of the average acceleration vector

- #2

lewando

Homework Helper

Gold Member

- 1,352

- 138

- #3

- 6

- 0

So far I have...

a) On any given clock, from 6PM to 9PM, the minute hand is 20cm. So applying a^2+b^2=c^2 with a= 20cm and b=20cm...I get the displacement value of 28.2842cm

b) average velocity = Δd/Δt = 28.2842/(3-0) =9.4280 cm/h

c) average acceleration = vf-vi/ tf-ti = (0.1571cm/s) / (3hrs) = 0.0008cm/s^2

d) magnitude = 28.2842cm

direction is tan^-1 (-20/-20) = 45°

- #4

lewando

Homework Helper

Gold Member

- 1,352

- 138

For a) you have found the magnitude.

For b) the average velocity vector is defined as the displacement vector divided by time. I think the question is implying time to be 15 minutes.

For c) the average acceleration vector formula is similar to what you have except that v

For d) you first need to find c).

- #5

- 6

- 0

the displacement of the clock moving the minute hand (20cm) from 6pm to 9pm is equal to the parimeter of the circle from 6pm to 9pm

P=2∏r = 2∏(20) = 40∏= 125.60

then i will have to divide by 4 to get the perimeter of a 6pm to 9pm = 31.4cm

so for a) the answer would be 31.4 cm

b) the average velocity vector would be 31.4/(15-0) = 2.0933cm/min = 0.0348cm/second = 0.0003488 m/s

c) i am not sure how to find the speed of the arrow tip of the minute hand at time t=6pm and t=9pm

d) i cannot solve d since i am not sure on how to solve part c)

thanks a lot for your help, i really appreciate it

- #6

- 36,163

- 6,782

No, you already found the correct magnitude (of the displacement). But the questions asks for a vector, so you also need to specify its direction. And it asks for this in 'unit vector notation'. Presumably you know what that means?a) since i have found the magnitude, i will need to find the displacement

There's no point in looking at b c and d until that's clear.

Share: