Question 1.1
Corvette speeds up quickly3 NJIT Physics 1: General Motors
mistakenly calls a car fast even it its only going 60 mi/hr. The
ads mean that it speeds up quickly. Thats acceleration.
2015 Chevy Corvette Z062015 BMW M1 Concept CarGeneral Motors has
released the initial performance results of 2015 Chevrolet Corvette
Z06, making it the fastest car GM has ever made. The new 'vette
accelerates from a full stop to 60 mph in a record-breaking 2.95
seconds.
How fast doesa Corvette accelerate?According to a GM ad, the
2015 Corvette hits 60 mph in 2.95 seconds. What is its acceleration
(in m/s/s)? 20.2; b. 10.1; c. 9.08; d. 4.532; e. none are close
Car and Driver
Skip the answers given andcreate a step by step
solution:SketchConvert v and t to standard units: List variables we
know and want: vo, v, t, a=?Pick the 2 physics equations:
Algebra:Arithmetic:Letter answer:Optional: Estimate the
uncertainty. Comment on the
numbers:60sec=1min1609m=1mi2.24mi/hr=1m/s0.0254m=1in
v=x/tBasic. (a isnt involved.) If needed, vave=(x-xo)/(t-to);
vave=(v+vo)/2a=v/tBasic. (x isnt involved.) Often: a=(v-vo)/t; 3.
x=vo*t+at2/2Comes from Eqs. 1&2. Handy if no v. 4.
v2=vo2+2axComes from Eqs. 3&4. Handy if no t.Step by step
solutionSketch
Units:v=60mph[(1m/s)/2.24mph]=26.8m/sList variables: v, t,
a=?Pick equations
v=x/tBasic. (a isnt involved.) If needed, vave=(x-xo)/(t-to);
vave=(v+vo)/2a=v/tBasic. (x isnt involved.) niOften: a=(v-vo)/t; 3.
x=vo*t+at2/2Comes from Eqs. 1&2. Handy if no v. 4.
v2=vo2+2axComes from Eqs. 3&4. Handy if no t.v=60mph
v=0 0 t=2.95s
AccelerationIs slopeStep by step answer cont.5.
Algebra:noneArithmetic: a=(26.8-0)[m/s]/2.95s=9.08m/s/sAnswer:
c.
Comments: Uncertainty in speed is about 0.1%, in t is
[.01/2.95]=0.3%, so a is uncertain by about 0.3%. The a is probably
between 9.05 and 9.11m/s/s.The car speeds up quickly.Acceleration
is important. When?
A reminder: Learn the stuff in chapter 2Heres how to do it: Dont
miss a class.Do the homework on the web its good practice for the
exam. Use the step by step method.Do the practice problems in the
syllabus it really is good practice. Use the step by step
method.
