# Basic motion stuffs, time and velociton

1. Mar 6, 2005

### k3l

Basic motion stuffs, time and velociton :(

hi
oh my gosh... i can't believe i forgotten how to do this...
i have to work out the time when will the two particles meet... where one particle (A) is travelling at a velocity of 80km/h, and (B) is travelling with a velocity of 100km/h while (B) is 350km behind (A)
(assume they are travelling toward the same directions)

thx

2. Mar 6, 2005

### snow

$$s_a = s_b$$
$$s_a = s_0 + v_a * t$$
$$s_b = v_b * t$$

Insert both in first equation and calculate t.

3. Mar 6, 2005

### moose

Basic algebra.

Distance=rate x time

D1=x
D2=x+350
so for the equation distance = rate x time just plug in x and x+350 as your distance, use t for time
since x is the same value, you can combine the two and solve for t.

4. Mar 6, 2005

### DB

I'm a bit confused, do you add the 2 distances?
$$x+x+350=100 \\ or \\ 80? *t?$$
Maybe I'm stupid but I'm confused...

5. Mar 6, 2005

use relative time frames. Take the moving particles frame that is behind the other particle, subtract the other cars speed and no consider that the other particle is stationary.

$$V_{slower\ particle} = 80km/h$$
$$V_{faster\ particle} = 100km/h$$
$$V_{faster\ particle\ relative\ to\ slower\ one} = 100km/h - 80km/h = 20km/h$$

use:

$$d = Vt$$

you should know what to sub in where.

Regards,