- 25 Sep '10 01:35 / 3 edits

Car A is passing Car B, however a few moments later Car B will pass Car A.*Originally posted by clandarkfire***Two cars emerge side by side from a tunnel. Car A is traveling with a speed of 60 km/h and has an acceleration of 40 km/h/min. Car B has a speed of 40 km/h and an acceleration of 60 km/h/min. Which car is passing the other as they come out of the tunnel? Explain.**

Explination:

dX_A/dt >dX_B/dt for t < 2 min

dX_A/dt<dX_B/dt for t>2 min - 25 Sep '10 06:14 / 1 edit

Duh, you just SAID they are side by side leaving the tunnel*Originally posted by clandarkfire***Two cars emerge side by side from a tunnel. Car A is traveling with a speed of 60 km/h and has an acceleration of 40 km/h/min. Car B has a speed of 40 km/h and an acceleration of 60 km/h/min. Which car is passing the other as they come out of the tunnel? Explain.** - 25 Sep '10 18:59But as far as I can see, Joe Shmo is right.

Next:

A speeding motorist travels past a stationary police officer at a speed of 120km/hr. The officer immediately begins pursuit at a constant acceleration of 10km/hr/s.

a. How long will it take for the police officer to reach the speeder, assuming the speeder maintains a constant speed?

b. How fast will the officer be traveling at that time? - 26 Sep '10 12:18

a. 24 seconds*Originally posted by clandarkfire***But as far as I can see, Joe Shmo is right.**

Next:

A speeding motorist travels past a stationary police officer at a speed of 120km/hr. The officer immediately begins pursuit at a constant acceleration of 10km/hr/s.

a. How long will it take for the police officer to reach the speeder, assuming the speeder maintains a constant speed?

b. How fast will the officer be traveling at that time?

b. 240 km/h - 27 Sep '10 07:50 / 2 edits

It's useful to know the formula:*Originally posted by clandarkfire***Por qué?**

It's probably pretty simple, but I'm just learning how to do this and don't want to come across as stupid.

Distance travelled = start_distance + start_speed*time + 0.5*acceleration*time**2

At the point of interception the Police officer and the motorist must have travelled the same distance. - 27 Sep '10 16:04 / 2 editsFor the police officer I used s = 1/2 at², and for the other one I used s = v t.

a = 10 km/h/s

v = 120 km/h

s = s

1/2 × 10t² = 120t

5t² - 120t = 0

5t × (t - 24) = 0

t = 0 or t = 24

In 24 seconds, the police officer drives at 10 × 24 = 240 km/h

Note:

s = 1/2 at²

v = at = s'

a = v' = s'' - 27 Sep '10 17:05

Regardless of their accelerations the current fastest car will pull ahead.*Originally posted by clandarkfire***Two cars emerge side by side from a tunnel. Car A is traveling with a speed of 60 km/h and has an acceleration of 40 km/h/min. Car B has a speed of 40 km/h and an acceleration of 60 km/h/min. Which car is passing the other as they come out of the tunnel? Explain.**