L O.

asked • 07/04/14

speed c/o physical science

1.  a car is traveling north on a road at a speed of 10 meters per second.  it hits from behind another car which is at rest and the two cars stick together.  what can be concluded from this information?
 
a.  the collision was elastic.   I say no to answer a
b.  the two cars stuck together will move to the north at a speed less than 10 meters
c.  the two cars stuck together will move to the north at a speed more than 10 meters per second.  i think this is the answer
d.  momentum was not conserved in the collusion
 
2.  a car traveling 30 k/h suddenly speeds up to 60 k/h.  what can you conclude from this information?
 
a.  there was a change in the potential energy of the car  ( I don't think this is the answer since energy does not double)
b.  no work (in its scientific meaning) was done on the car
c.  the car will take four times longer to come to a complete stop
d.  all of these
 
 

2 Answers By Expert Tutors

By:

Alexander F. answered • 07/04/14

Tutor
New to Wyzant

Patient and Passionate University of South Florida Math/Science Tutor

Michael A.

Answer b is incorrect.  Please see my response below.  Questions are sometimes not clear in the use of "long," which can be used to mean TIME or DISTANCE.
 
By the Work-Kinetic Energy Theorem, W=change in KE.  Since KE=1/2mv^2, and v changes, then there must have been work done on the car.  Also, this theorem can be used to show that the distance needed to stop is 4 times as "LONG."
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07/04/14

Michael A. answered • 07/04/14

Tutor
New to Wyzant

Math/Physics/Science Tutor

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