- Joined
- 10 Dec 06
- Moves
- 8528
25 Sep 10
3 edits
Originally posted by clandarkfireCar A is passing Car B, however a few moments later Car B will pass Car A.
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
1 edit
Originally posted by clandarkfireDuh, you just SAID they are side by side leaving the tunnel🙂
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
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?
26 Sep 10
Originally posted by clandarkfirea. 24 seconds
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
- Joined
- 26 Apr 03
- Moves
- 26771
27 Sep 10
2 edits
Originally posted by clandarkfireIt's useful to know the formula:
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
2 edits
For 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
Originally posted by clandarkfireRegardless of their accelerations the current fastest car will pull ahead.
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.