- #1

ilovemynny

- 24

- 0

## Homework Statement

The Known Facts of the Accident

[1] Ned was traveling North on Oak Avenue in his car of mass 2000kg

[2] Ed was traveling East on King Street in his truck of mass 3000 kg

[3] The two approached the intersection at the same moment.

[4] With his stoplight “green”, Ned had the right-of-way and entered the intersection.

[5] Ed admitted that he failed to stop for the light and entered the intersection at the same moment as Ned.

[6] The collision occurred in the middle of the intersection.

[7] Both cars locked together upon impact and slid to a stop.

[8] From the point of impact (determined by shattered headlights on the pavement), the cars traveled a distance of 6.0 meters along a line that measured 40o North of East.

[9] From data tables in their accident investigation manuals, the investigators determined that the coefficient of friction between the road and the sliding cars was 1.5

Questions to Be Answered

[A] Considering the road surface to be horizontal, what was the frictional force that acted upon the locked sliding cars to stop them?

**What was the magnitude of the acceleration that this force produced on the sliding cars sliding together?**

[C] Based upon the stopping distance from the point of impact and the acceleration, what was the speed of the two locked cars at the moment after the impact?

[D] What was the momentum of the two locked cars at the moment after the impact?

[E] What part of this momentum did Ed contribute? (this would be his momentum before impact)

[F] What part of this momentum did Ned contribute?

[G] What was Ed’s speed before the collision?

[H] What was Ned’s speed before collision?

[C] Based upon the stopping distance from the point of impact and the acceleration, what was the speed of the two locked cars at the moment after the impact?

[D] What was the momentum of the two locked cars at the moment after the impact?

[E] What part of this momentum did Ed contribute? (this would be his momentum before impact)

[F] What part of this momentum did Ned contribute?

[G] What was Ed’s speed before the collision?

[H] What was Ned’s speed before collision?

*The speed limit at the intersection was 35 mi/hr. The police will ticket drivers for speeding if they exceeded the speed limit by more than 5 mi/hr. Should either of the two drivers be ticketed for speeding? Defend your answer with calculations.*

So these are the questions I've already got to:

My Work:

A) To find the friction force I used this formula: Ff = coefficient of friction x mass x 9.81

So my friction force came out to be 73575 N which turned into 70,000 N because of significant numbers.

B) F = m x a so 70000 = 5000a and a = 14 m/s/s

C) vf^2 = vi^2 + 2ad

vf^2 - vi^2 = 2ad

vf^2 = 2 x (14)(6)

vf^2 = 168

vf = 12.96

vf = 13 m/s

D) Momentum: P = m x v

P = (2000 + 3000) kg x (13 m/s)

P = 65000 kg m/s

E) Momentum of Ed: P = m x v

P = 3000 kg x 13 m/s

Ed: P = 39000 kg m/s

F) Momentum of Ned: P = m x v

P = 2000 kg x 13 m/s

Ned: P = 26000 kg m/s

I just don't know how to find their initial speed?

And I feel like I didn't do E and F right.

Please someone help!## Homework Equations

## The Attempt at a Solution

So these are the questions I've already got to:

My Work:

A) To find the friction force I used this formula: Ff = coefficient of friction x mass x 9.81

So my friction force came out to be 73575 N which turned into 70,000 N because of significant numbers.

B) F = m x a so 70000 = 5000a and a = 14 m/s/s

C) vf^2 = vi^2 + 2ad

vf^2 - vi^2 = 2ad

vf^2 = 2 x (14)(6)

vf^2 = 168

vf = 12.96

vf = 13 m/s

D) Momentum: P = m x v

P = (2000 + 3000) kg x (13 m/s)

P = 65000 kg m/s

E) Momentum of Ed: P = m x v

P = 3000 kg x 13 m/s

Ed: P = 39000 kg m/s

F) Momentum of Ned: P = m x v

P = 2000 kg x 13 m/s

Ned: P = 26000 kg m/s

I just don't know how to find their initial speed?

And I feel like I didn't do E and F right.

Please someone help!