# PHYSICS 231 CHAPTERS 1-4 TEST

Name ________________________
September 18, 2002

1in=2.54cm; v=v0 + at; a*b=a b cos q; a=v2/r; Earth radius=6380km
1mi=1.61km; x - x0=v0t + 1/2 a t2; a x b=a b sinq; T=2pr/v; proton mass=1.6x10-27 kg
VSPHERE=4/3pr3; v2=v02 + 2 a (x - x0); dx/dt=v; HINT: Do the easy problems first!
ASPHERE=4pr2; x - x0=1/2(v0 + v) t; dv/dt=a; 1 cm3 water=1 gm; 1 kg=2.2 lb;

Multiple Choice (do all)
1) You measure the radius of a wheel to be 4.16 cm. If you multiply by 2 to get the diameter, how should you express the result?
A) 8 cm B) 8. cm C) 8.3 cm D) 8.32 cm E) 8.320 cm

2) A cubical box is said to be 38cm +/- 1cm on each side. What percent uncertainty does that make in the volume of the box?
A) 0.07% B) 1.8% C) 2.6 % D) 5.2% E) 7.8%

3) While moving to Huntsville, I drove my loaded Ryder truck over the Appalachians near Roanoke, Va. With my foot to the floor I managed 35 mph going uphill for 10 miles, and 65 mph going downhill for 10 miles. What was my average speed?
A) 40 mph B) 45 mph C) 50 mph D) 55 mph E) 60 mph

4) A baseball is thrown vertically into the air. What is the acceleration, a, and velocity, v, of the ball at its highest point?
A) a=max, v=max B) a=0, v=max C) a=0, v=max D) a=0, v=0 E) Not enough information

5) Which of the following are scalars: i) acceleration, ii) velocity, iii) speed, iv) distance, v) displacement
A) i B) i,ii,iii C) ii, iii D) iii,iv E) iv,v

6) Two rowers, who can row at the same speed in still water, set off across a river at the same time. Alice heads straight across and is pulled downstream somewhat by the current. Bob heads upstream at an angle so as to arrive at a point opposite to the starting point. Which rower reaches the opposite side first?
A) Alice B) Bob C) Neither, it's a tie D) Not enough information

7) My 6 year-old can throw a baseball vertically 3 meters. If my 11 year-old can throw the same ball twice as fast, how high will it go?
A) four times as high B) thrice as high C) twice as high D) 1.4 times as high E) not enough info

8) A full cup of water is sliding down a very long but frictionless (barely) inclined plane when the angle is steepened by gradually lifting up the high end. Does the water in the cup
A) slosh out the front B) slosh out the back C) not slosh at all D) not enough information

9) Neil Armstrong weighed himself before launch on a bathroom (spring) scale and a doctor's (2-pan balance) scale and found that they both gave his weight as 66 kg. When he arrived on the moon, he weighed himself on both scales again and found,
A) both scales agreed that he weighed 11 kg
B) the spring scale said 11kg, the pan balance said 66 kg
C) the spring scale said 66kg, the pan balance said 11 kg
D) both scales agreed that he weighed 66 kg
E) the scales didn't work at all since he floated off them.

10) If vector B is added to vector A the result is 6.0i + 2.0j. If B is subtracted from A, the result is -4.0i + 7.0j. What is the magnitude of A?
A)1.0 B) 4.6 C) 6.3 D) 8.0 E) 9.2

Problems (do all 4, use back of sheet for diagrams)
1) Francesca was flying out of O'Hare and was so bored waiting on the tarmac that she devised a plumb bob with her watch and a strand of hair. When the plane finally accelerated down the runway, she noticed that the watch was hanging 20 degrees from the vertical and did so for 20 seconds before the plane got airborne. What was the takeoff speed of the plane?

2) Because the Earth rotates once per day, the effective acceleration of gravity at the equator is slightly less than it would be if the Earth didn't rotate. What is the percentage change in gravity caused by this effect?

3) A baseball is seen to pass upward by a window 21m above the street with a vertical speed of 17 m/s. If the ball was thrown from the street, (a) what was its initial speed, (b) what altitude does it reach, (c) when was it thrown, and (d) when does it reach the street again?

4) Noah's ark was ordered to be 300 cubits long, 50 cubits wide and 30 cubits high. The cubit was a unit of measure equal to the length of the human forearm, elbow to the tip of the longest finger. Estimate the number of animals that could fit on the ark if they were all the size of a cat. Now estimate the number of animals if one had to keep them fed for 400 days.

Extra Credit
5) A small block of mass m rests on the sloping side of a triangular block of mass M which itself rests on a horizontal table as shown below. Assuming all surfaces are frictionless, determine the force F that must be applied to M so that m remains in a fixed position relative to M (that is, m doesn't move on the incline.)
m F M (