Police car and speeder when do they meet?

  • Thread starter endeavor
  • Start date
  • Tags
    Car
In summary: At time t = -0.9307, the officer has moved from x0p to x0s and the speeder has also moved from v0s to v0p.
  • #1
endeavor
176
0
Homework Statement
An unmarked police car traveling a constant 95km/h is passed by a speeder traveling 140 km/h. Precisely 1.00s after the speeder passes, the policeman steps on the accelerator; if the police car's acceleration is 2.00m/s2, how much time passes before the police car overtakes the speeder (assumed moving at constant speed)?

v0p = 95 km/h = 26.389 m/s
v0s = 140 km/h = 38.889 m/s
ap = 2.00 m/s
t1 = 1.00 s
vs = v0s

Homework Equations


x = x0 + v0t + 0.5 * a * t2

The Attempt at a Solution


Let t2 = the time it takes them to meet after the initial 1.00s.
After 1.00s, the xp = 26.389m and xs = 38.889m. Taking these two quantities as our initial positions, x0p and x0s, we have:
xp = x0p + v0pt2 + 0.5 * ap * t22
xs = x0s + v0st2
Setting these two equal, I get a quadratic equation and find t2 = 13.43 s or -0.9307 s. The total time would then be 14.43s...

But wait. Shouldn't the negative answer for t2 be -1.00s?? Because 1.00s in the past, the cars met... So I must be doing something wrong...
 
Physics news on Phys.org
  • #2
endeavor said:
But wait. Shouldn't the negative answer for t2 be -1.00s?? Because 1.00s in the past, the cars met... So I must be doing something wrong...
Firstly, nice presentation :approve: Secondly, don't forget from 0.00s to 1.00s the police car wasn't accelerating, so the symmetry is slightly misleading.
 
  • #3
Hootenanny said:
Firstly, nice presentation :approve: Secondly, don't forget from 0.00s to 1.00s the police car wasn't accelerating, so the symmetry is slightly misleading.

What do you mean "the symmetry is slightly misleading"?

Is my answer correct or wrong?
 
  • #4
Your method looks correct, but I ain't checking the math for you. The symmetry is misleading because t = -0.9307 would have been the time they would have met if the police car would have been accelerating from t = 0.

Does that make sense?
 
  • #5
Hootenanny said:
Your method looks correct, but I ain't checking the math for you. The symmetry is misleading because t = -0.9307 would have been the time they would have met if the police car would have been accelerating from t = 0.

Does that make sense?
Oh I see...
I forgot about that.

thanks :approve:
 
  • #6
Pleasure, once again great presentation.
 
  • #7
i cannt understand it
 
  • #8
The position of the police officier is a piece-wise function.
 

FAQ: Police car and speeder when do they meet?

How do police cars and speeders determine the speed limit at which they will meet?

Police cars and speeders generally meet at the speed limit that is set on a specific road or highway. This speed limit is determined by factors such as road conditions, traffic patterns, and safety considerations. Additionally, police officers may use radar guns or other speed-monitoring devices to determine the speed of a vehicle, which can also impact when they will meet a speeding car.

Is there a specific distance or time at which police cars and speeders will meet?

The distance or time at which police cars and speeders will meet can vary depending on a variety of factors. This can include the speed of the vehicles, the distance between them, and any obstacles or traffic that may impact their speed. In general, the faster the speed of the vehicles, the shorter the distance or time it will take for them to meet.

What happens when a police car and speeder meet on the road?

When a police car and speeder meet on the road, the police officer may choose to pull over the speeding vehicle and issue a citation for breaking the speed limit. The speeder may also be subject to other consequences, such as fines or points on their driving record. In some cases, the police officer may also choose to give a warning instead of a citation.

Are there any factors that can affect when a police car and speeder will meet?

There are several factors that can affect when a police car and speeder will meet on the road. These can include the speed of the vehicles, the distance between them, any obstacles or traffic on the road, and the reaction time of the police officer. Additionally, weather and road conditions can also impact the speed at which a vehicle is traveling and therefore affect when they will meet.

Can a police car and speeder meet at a different location than originally intended?

Yes, a police car and speeder can meet at a different location than originally intended. This can happen if one of the vehicles changes their speed or direction, or if there are any unexpected obstacles or traffic on the road. It is also possible for the police officer to choose to pursue the speeding vehicle and meet them at a different location in order to issue a citation or warning.

Similar threads

How Long for a Police Car to Catch a Speeder?
Replies
11
Views
1K
How far does the police car travel to catch a speeder traveling at 180 km/hr?
Replies
1
Views
1K
Speeder and Cop Meeting Time Calculation
Replies
11
Views
3K
Police Car Overtaking Speeder: How to Calculate the Time and Distance?
Replies
1
Views
2K
How Long Does It Take for a Police Car to Catch a Speeder?
Replies
3
Views
3K
Motorcycle Police Officer Chasing Car
Replies
18
Views
7K
Solving for Time: Police Car Catches Speeder
Replies
1
Views
2K
How Long Does It Take for a Police Car to Catch a Speeder?
Replies
8
Views
7K
Many failed attempts on this displacement/acceleration/velocity problem.
Replies
1
Views
2K
Catching the Speeder: Police Car Velocity & Distance Traveled
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top