95ICHS (1) m,v, = (m, + m,) Apply the isolated system model for momentum in the y-direction: (2) mzv2 sin e Divide Equation (2) by Equation (1):

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Collision at an Intersection
A 1,550 kg car traveling east with a speed of 28.1 m/s collides at an intersection with a 2,550 kg truck traveling north at a speed of 20.3 m/s as shown in the figure. Find the direction and magnitude of the velocity of the wreckage
after the collision, assuming the vehicles stick together after the collision.
SOLUTION
Conceptualize The figure should help you conceptualize the situation before and after the collision. Let us choose east to be along the positive x-direction and north to be along the positive y-direction.
In what direction is the blue car moving initially?
O to the north
O to the south
O to the east
O to the west
Categorize Because we consider moments immediately before and immediately after the collision as defining our time interval, we ignore the small effects that friction would have on the wheels of the vehicles and model the two
vehicles as an isolated system in terms of momentum. We also ignore the vehicles' sizes and model them as particles. The collision is perfectly inelastic
vV because the car and the truck stick together after the collision.
Analyze Before the collision, the only object having momentum in the x-direction is the car
Therefore, the magnitude of the total initial momentum of the system (car plus truck) in the x-direction is that of only the
car. Similarly, the total initial momentum of the system in the y-direction is that of the truck
After the collision, let us assume the wreckage moves at an angle e with respect to the x-axis with speed vr
(For the next three answers, use the following as necessary: m,, m2, Vr, and 0. Do not substitute numerical values; use variables only.)
Apply the isolated system model for momentum in the x-direction:
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9/14
9.5I CH9 - Active Tutorial EC3 - PHY2048 12-WEEKS, section 2048-8 ONLINE, Fall 2021 I WebAssign
Ap, -0-P -EPat
(1) m,v- (m, + m2)
Apply the isolated system model for momentum in the y-direction:
Ap, = 0-Py -Pyr
(2) mzv2 =
sin 0
Divide Equation (2) by Equation (1):
Transcribed Image Text:Collision at an Intersection A 1,550 kg car traveling east with a speed of 28.1 m/s collides at an intersection with a 2,550 kg truck traveling north at a speed of 20.3 m/s as shown in the figure. Find the direction and magnitude of the velocity of the wreckage after the collision, assuming the vehicles stick together after the collision. SOLUTION Conceptualize The figure should help you conceptualize the situation before and after the collision. Let us choose east to be along the positive x-direction and north to be along the positive y-direction. In what direction is the blue car moving initially? O to the north O to the south O to the east O to the west Categorize Because we consider moments immediately before and immediately after the collision as defining our time interval, we ignore the small effects that friction would have on the wheels of the vehicles and model the two vehicles as an isolated system in terms of momentum. We also ignore the vehicles' sizes and model them as particles. The collision is perfectly inelastic vV because the car and the truck stick together after the collision. Analyze Before the collision, the only object having momentum in the x-direction is the car Therefore, the magnitude of the total initial momentum of the system (car plus truck) in the x-direction is that of only the car. Similarly, the total initial momentum of the system in the y-direction is that of the truck After the collision, let us assume the wreckage moves at an angle e with respect to the x-axis with speed vr (For the next three answers, use the following as necessary: m,, m2, Vr, and 0. Do not substitute numerical values; use variables only.) Apply the isolated system model for momentum in the x-direction: https://www.webassign.net/web/Student/Assignment-Responses/lastdep-26947395 9/14 9.5I CH9 - Active Tutorial EC3 - PHY2048 12-WEEKS, section 2048-8 ONLINE, Fall 2021 I WebAssign Ap, -0-P -EPat (1) m,v- (m, + m2) Apply the isolated system model for momentum in the y-direction: Ap, = 0-Py -Pyr (2) mzv2 = sin 0 Divide Equation (2) by Equation (1):
Solve for e (in degrees counterclockwise from the +x-axis) and substitute numerical values:
O - tan- m22i
m,V
° counterclockwise from the +x-axis
Use Equation (2) to find the value of v, and substitute numerical values (Enter the magnitude in m/s.):
> m/s
(m, + m,)sin e
Finalize Notice that the final speed of the combination is less than the initial speeds of the two cars. This result is consistent with the kinetic energy of the system being reduced in an inelastic collision. It might help if you draw the
iete io
EXERCISE
The eastbound car in the example is driven by an off-duty police officer, who knows her speed was exactly 20.0 m/s. From studying the angle e (and the mass of the two vehicles), she concluded that the truck was over the speed
limit of 80 km/h driving on that secondary road. Of course, the truck also failed to stop before entering the main road. If the truck were not speeding, what should be the maximum angle for e (in degrees counterclockwise from the
+x-axis) in this accident?
Hint
tps://www.webassign.net/web/Student/Assignment-Responses/last'dep-26947395
10/1
1/5/21, 5:30 PM
9.5I CH9 - Active Tutorial EC3 - PHY2048 12-WEEKS, section 2048-8 ONLINE, Fall 2021 I WebAssign
es 49.91
Use your diagram and the relations between the components of velocity before and just after collision to find the angle. counterclockwise from the +x-axis
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Transcribed Image Text:Solve for e (in degrees counterclockwise from the +x-axis) and substitute numerical values: O - tan- m22i m,V ° counterclockwise from the +x-axis Use Equation (2) to find the value of v, and substitute numerical values (Enter the magnitude in m/s.): > m/s (m, + m,)sin e Finalize Notice that the final speed of the combination is less than the initial speeds of the two cars. This result is consistent with the kinetic energy of the system being reduced in an inelastic collision. It might help if you draw the iete io EXERCISE The eastbound car in the example is driven by an off-duty police officer, who knows her speed was exactly 20.0 m/s. From studying the angle e (and the mass of the two vehicles), she concluded that the truck was over the speed limit of 80 km/h driving on that secondary road. Of course, the truck also failed to stop before entering the main road. If the truck were not speeding, what should be the maximum angle for e (in degrees counterclockwise from the +x-axis) in this accident? Hint tps://www.webassign.net/web/Student/Assignment-Responses/last'dep-26947395 10/1 1/5/21, 5:30 PM 9.5I CH9 - Active Tutorial EC3 - PHY2048 12-WEEKS, section 2048-8 ONLINE, Fall 2021 I WebAssign es 49.91 Use your diagram and the relations between the components of velocity before and just after collision to find the angle. counterclockwise from the +x-axis Need Help? Read It
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