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100% Correct Answers.
Study of an automobile collision requires which of the following topics in physics? - Correct Ans: ✔✔Newtonian mechanics Which of the following is a fundamental unit of the International System of Units? - Correct Ans: ✔✔Second If x is measured in meters, v and vo in m/s and a in m/s2, which of the following is NOT dimensionally consistent? - Correct Ans: ✔✔x = ½ at+vot The prefix for one one-thousandth (10-3) is - Correct Ans: ✔✔milli Express .052 g in engineering notation. - Correct Ans: ✔✔52 mg A man goes out for a walk. He first walks 120 m and then rests. He then continues on his walk for another 64.8 m. What is the total length of his walk? - Correct Ans: ✔✔185 m What is the circumference of a circle with a 7.38 cm radius? (carefully consider the number of significant figures) - Correct Ans: ✔✔46.4 cm
Convert 0.092 kg to standard units - Correct Ans: ✔✔92 g Convert 211.3 s to minutes. - Correct Ans: ✔✔3.522 min Divide 46.73/11 and determine the answer in significant figures. - Correct Ans: ✔✔4. A squirrel dashes across a 240 cm wide road in 0.075 minutes. (You must always show work on any Free Response Question. Most points are awarded for showing the work and not for the actual answer.) A. Convert both values to standard units. B. Using the equation speed=distance/time calculate the speed using significant figures. C. Convert the answer to Engineering Notation. - Correct Ans: ✔✔A. 240cm(1m/100cm)=2.4m 2 Points 0.075min(60s/1min)=4.5s 2 Points B. 2.4/4.5=0.5333 2 Points 0.53 m/s 2 Points C. 530 x 10-3 2 Points Given two vectors: A=4i+ 2j and
A woman runs 450 m at 30.o. Assuming the angle is measured from normal compass points how far North did she get? - Correct Ans: ✔✔390 m North would be the x component and standard angle values are given from positive x or East. Ay=Asin() Ay=450sin(30)= if you got 69 then your calculator is in radians and should be in degrees Three sticks of length 6.0 cm, 8.0 cm and 10.0 cm are assembled into a right triangle. What is the angle of the where the 6.0 cm stick connects to the 10.0 cm stick? - Correct Ans: ✔✔ 53 º T-6.0 cm becomes the adjacent side so cosθ=(6/10) θ=cos-1(86/10)=53o or 3- 4 - 5 triangle so Pythagorean triple, with angles of 53º and 37º.
Which equation represents the angle θ in the drawing? - Correct Ans: ✔✔cos^-1(3/7)
- 3 is adjacent, 7 is hypotenuse, cos θ = adjacent over hypotenuse. θ = cos-1(3/7)=65o Given the vector relationship A + B = C. If the magnitudes of the vectors are related by A + B > C which of the following statements are true? (Choose all that are correct) - Correct Ans: ✔✔The vectors A and B could NOT be pointing in the same direction A dog walks 25.0 m West and then 7.50 m North. What is the magnitue of the sum of these two vectors? - Correct Ans: ✔✔26.1 m R=sqrt(Ax2+Ay2) R=sqrt(252+7.52)=26.1 m A dog walks 25.0 m East and 7.50 m South. What is the angle of the sum of these two vectors? - Correct Ans: ✔✔-16.7o ()=tan-1(Ay/Ax) ()=tan-1(-7.5/25)=-16.7o
Force is measure in Newtons (kgm/s2), acceleration in m/s2, and mass in kilograms. Which of the following equations would be dimensionally correct? - Correct Ans: ✔✔F=ma The prefix for one thousand (103) is - Correct Ans: ✔✔kilo A student carefully measures the time it takes for a turtle to move 10. m. He gets a value of 4218.6 s. However he discovers that the stopwatch had already been running for about 300 s before the turtle started to move. How long did it take the turtle to go 10.0 m? - Correct Ans: ✔✔3900 s What is the circumference of a circle with a 7.38 cm radius? (carefully consider the number of significant figures) - Correct Ans: ✔✔Correct answer: 46.4 cm Convert 0.092 kg to standard units - Correct Ans: ✔✔0.092 kg Convert 19.2 hours to minutes. - Correct Ans: ✔✔1150 min Subtract 46.73 - 11 and determine the answer in significant figures. - Correct Ans: ✔✔ 36
In addition and subtract we determine the significant digits by the significant columns in the original numbers. 46.73 is significant to the 1/100th's column and 11 to the 1's column. The answer can only be significant to the 1's column. 36 When adding two vectors with magnitudes A and B that are pointing along the same axis which of the following are possible values for the magnitude of the resultant vector? (Please choose all correct answers) - Correct Ans: ✔✔R=A-B R=A+B Which of the following is/are vectors? (Choose all that are correct) - Correct Ans: ✔✔The speed and direction of a bullet headed for a target The information needed to catch a moving ball A submarine is travels 32500 m but only goes 9250 South. What is the angle of the subs displacement relative to East? - Correct Ans: ✔✔- 16.5o
A dog walks 25.0 m East and 7.50 m South. What is the angle of the sum of these two vectors? - Correct Ans: ✔✔Correct answer:
- 16.7o A cat covers a distance of 31800 mm in 0.0450 hours. A. Convert the distance to standard units. B. Convert the time to standard units. C. What is the cat's average speed in meters per second during this time period? - Correct Ans: ✔✔A. d=31800 mm(1m/1000mm) 1 Point d=31.8m 1 Point B. t=0.0450 hr(60min/hr)(60s/min) 1 Point t=162s 1 Point C. s=d/t 1 Point s=31.8/162 1 Point s=0.196m/s 2 Point Reasonable Sig Figs (2-4) 1 Point Correct units for all 3 answers 1 Point Add the following vectors. A 3.75 m at 34.7o West of North B 8.31m East - Correct Ans: ✔✔A=3.75 θA=124.7 1 Point B=8.31 θB=0 1 Point
Ax=Acosθ=(3.75)cos(124.7)=-2.13 1 Point Ay=Asinθ=(3.75)sin(124.7)=3.08 1 Point Bx=Bcosθ=(8.31)cos(0)=8.31 1 Point By=Bsinθ=(8.31)sin(0)=0 1 Point Rx=Ax+Bx=(-2.13)+8.31=6.18 1 Point Ry=Ay+By=3.08+0=3.08 1 Point R=√(Rx2+Ry2)=√(6.18)2+(3.08)2)=6.90m 1 Point θ=tan-1(Ry/Rx)=tan-1(3.08/6.18)=26.5o θ=26.5o (implied from +x) 1 Point or 26.5o North of East Which of the following is the correct relationship between distance and the magnitude of displacement as an object moves from point A to point B along the curved path shown? - Correct Ans: ✔✔The distance is greater than the magnitude of the displacement What is the displacement of a particle that has a position versus time of x(t) = t3-3t from t= 1.0 s to the particle's final position at t=3.0s? - Correct Ans: ✔✔ 20 A sprinter running in a straight line passes through two gates in 2. seconds. If the first gate is a displacement of 10.0 meters from the starting line, and the second gate is a displacement of 30.0 meters from
x=v0t+1/2at v0 is zero so x=1/2at x/t2=a/2 and a/2 is a constant so x/t2=x'/(2t) x'=(2t)2x/t2=4t2x/t2=4x A car traveling in a straight line at 14 m/s when the driver puts on the brakes and comes to a top in 35 s. What is the average acceleration of the car while it is braking? - Correct Ans: ✔✔-0.40 m/s v0=14, v=0 (stops), t=35, a=? v=v0+at a=(v-v0)/t a=(0-14)/35=-0.400 m/s A car accelerates at 3.00 m/s2 so that its displacement is 15.0 m after 2.0s. What was the initial velocity of the car? - Correct Ans: ✔✔4.5 m/s v0=?, x=15, t=2, a= x=v0t+1/2at 15=v(2)+1/2(3)(2)
15=2v+ 15 - 6=9=2v v=4.5 m/s A ball is observed to accelerate down a hill from 2.0 m/s to 10. m/s. The acceleration lasts for 5.0s. What is the displacement of the ball? - Correct Ans: ✔✔30. m v0=2, v=10, t=5, x=? x=1/2(v+v0)t x=1/2(2+10)5=30. m A ball is observed to accelerate down a hill from 2.0 m/s to 10. m/s. The acceleration is measured as 5.0 m/s2. How far does the ball roll? - Correct Ans: ✔✔9.6 m v0=2, v=10, x=?, a= v2=v02+2ax x=(v2-v02)/2a x=(102-22)/2(5)=9.6 m You are driving your car at a speed of 23.0 m/s and you hit the brakes. You skid to a stop. Upon measuring the skid marks, you find they are 85.0 meters long.
A rock is thrown vertically downward at an initial velocity of - 50. m/s. What is the velocity of the rock after 2.0 s? - Correct Ans: ✔✔-70. m/s v=v0+at v=(-50)+(-9.8)(2) v=-70. m/s A 10. kg rock is dropped from rest from a 79m tower. How long does it take for the rock to reach the ground? - Correct Ans: ✔✔4.0 s y=v0t+1/2at v0=
- 79=1/2(-9.8)t
- 158=-9.8t 16.1=t t=4.0s A rock is thrown vertically upward at an initial velocity of 50. m/s. What is the displacement of the rock when it has a velocity of - 20. m/s? - Correct Ans: ✔✔110 m v2=v02+2ay y=(v2-v02)/2a y=(202-502)/2(-9.8)
y=110 m Given a particle with the displacement versus time graph shown above, during which interval(s) is the velocity minimum? - Correct Ans: ✔✔C only Direction matters for velocity, delta v / delta t = (-3) / (+1) at C, which is less than (+2) / (+1) at D. Given a particle with the displacement versus time graph shown above, during which interval(s) is the velocity maximum? - Correct Ans: ✔✔D only Direction matters for velocity, delta v / delta t = (+2) / (+1) at D, which is greater than (-3) / (+1) at C. Given a particle with the displacement versus time graph shown above, what is the velocity of the particle at t = 4.5 s? - Correct Ans: ✔✔2. m/s Δx/Δt = 2/1 m/s = 2.0 m/s Using the v-t graph above, determine the average acceleration between t=4 and t=6s. - Correct Ans: ✔✔-4.5 m/s
a2 = 0 m/s2 1 point a1 = 3 m/s2 1 point Indication that student was considering area to find displacement. 2 points Correct positive area from 6-10s (OK if student cancelled 0-3 s with 7- 10 s areas): 6m 1 point Correct negative areas: - 13.5 m 1 point Correct total displacement of - 7.5 m 1 point Which of the following is the NOT a correct relationship between distance and the magnitude of displacement as an object moves from point A to point B along the curved path shown? - Correct Ans: ✔✔The distance is less than the magnitude of the displacement What is the displacement of a particle that has a position versus time of x(t) = t3-3t from t= 1.0 s to the particle's final position at t=3.0s? - Correct Ans: ✔✔ 20 displacement = final displacement - initial displacement = x(3s) - x(1s) = 18 - (-2) = 20 m A sprinter running in a straight line passes through two gates at a constant speed of 6 m/s. If the first gate is a displacement of 10. meters from the starting line, and the second gate is a displacement of 30.0 meters from the starting, how much time elapsed between when sprinter passed the first and second gates? - Correct Ans: ✔✔3.33 s
vavg = Δx/Δt = (30-10) / (t-0) = 6 m/s, t = 20/6 = 3.33 s In which one of the following cases does the car have a southward acceleration? - Correct Ans: ✔✔Traveling northward and slowing down. Cars A and B start at rest and travel with the same acceleration. Compare the speed of of car A to car B, after car A has traveled nine times the distance of B. - Correct Ans: ✔✔The problem said nothing about time, so you should think of v2=vo2+2ax, but vo=0. So with the same acceleration, v2 = 2ax = (constant) * x. v=√(con)x, square root of 9= For a car accelerating from rest, assuming all other variables remain unchanged, if you increased the acceleration from a to 2a you would expect the final velocity to increase from v to - Correct Ans: ✔✔2v v=v0+at v=at since v0= t=v/a v/a=2v/2a so the final velocity would be 2v
