Download Physics 1020 Practice Exam 1 Answers

Physics 1020 Practice Exam 1
While doing this exam, also try to define each term. Better understanding of the material comes from
complete understanding of terms given.
Chapter 1
1. Which of the following is not part of the three fundamental physical quantities?
a) Time b) Mass c) Volume d) Distance
2. A vector contains magnitude as well as direction, while scalar contains magnitude but not
direction.
3. Designate the following terms as either Scalar (with an S beside it) or Vector (with a V beside it).
Mass S
Weight V
Speed S
Velocity V
Force of friction V
Distance S
Acceleration V
Gravity V
Time S
Displacement V(Note:
Displacement is distance that has DIRECTION associated with it)
4. A) A graph is plotted with distance over time; the slope gives the velocity of the object.
B) A graph is plotted with velocity over time; the slope gives the acceleration of the object.
5. A person who has traveled eight kilometer was wondering how many meters they have traveled.
What is the answer? 8000m The same person is also wondering how many miles they have
traveled. What is the answer? 5 miles How much feet has this person traveled? (1m = 3.28 feet,
8000m = 26240feet)
6. The moon orbits around the earth every 27.3days. What is the frequency of which the moon does
a complete cycle? (answer in SI Units for frequency) 27.3days x 24hours x 60 minutes x
60seconds (converting days into seconds) f = 1/2358720 seconds or f = 1/2358720 Hz
7. For a car speeding on a highway, its tire has a period of 0.05s, what is the frequency?
f = 1/0.05s = 20Hz
8. On a very large ruler, a duck starts off at the 20m mark, and then rushes to the 83m mark in 3s.
What is the duck’s velocity?
a = change in velocity / change in time = 83m-20m/3s = 63m/3s = 21m/s
9. According to the graph below:
What are the velocities for the: While doing this problem, use the point (0,0) as your d1 and t1
. Slope = rise/run = (d2-d1)/(t2-t1)
a) Turtle 0.5m/s b) Human 1m/s c) Horse 2m/s
d) For the rocket, what is currently happening to its velocity? It is increasing What is this called?
acceleration
e) For the rolling ball, what is currently happening to its velocity? It is decreasingWhat is this
called? Deceleration What is the ball’s velocity between 4 and 5 seconds? 0m/s. Even though
1second has elapsed, no distance was covered.
10. Draw the resulting vectors of the following:
11. An object goes from 42m/s to 12m/s in 10s, what is its acceleration?
a = (v2 – v1)/t = (12m/s – 42m/s)/10s = (-30m/s)/10s = -3m/s2. This is decelerating
12. A ball is spinning on a string horizontally, and the diameter of the string is 24m. The velocity of
the ball is 6m/s. What is the centripetal acceleration of the ball? If diameter = 24m, radius =12m
a = v2/r = (6m/s)2/12m = 3m/s2
13. A boy, who’s on top of the building staring straight down, spits out his bubble gum. After 5s his
gum hits the ground. How high did the boy spit his gum from? He spits his gum, gravity is in
effect. acceleration due to gravity = 9.8m/s2 d = ½at2 = ½(9.8m/s2)(5s)2 = 122.5m
Chapter 2
Match the following:
A. Newton’s First Law
B A car hits a wall, and the heavier and faster the car is
B. Newton’s Second Law
accelerating, the stronger the force
C. Newton’s Third Law
A An object is currently floating in space, and nothing
is acting upon it. This object is stationary
C A person punches a wall, and feels tremendous
amount of pain in the fist.
1. An object which would normally weigh 63lbs at the surface of the Earth, of which is 6,000 miles
away from the center of the Earth, would weigh how much if the object was placed on a pillar
18,000 miles away?
W1 = 63lbs @ 6000miles. W2 = ?? @ 18000miles. 18000 miles is a factor 3 larger than
6000miles. According to Newton’s Universal Law of Gravitation, F is proportional to d2.
Since d is square, the factor of 3 becomes a factor of 9. That factor of 9 is taken away from
the original 63lbs. Therefore the person would weigh 7lbs 18000miles above the surface.
2. A gold bar, 10kg, is floating in space and is not near any object, planet, star, or black hole. What
is the gold bar’s weight if it were to somehow triple in mass? W = mg. Not near any source,
therefore no gravity. W = 0 N or 0 lbs.
3. A cement block is placed upon a tilted ramp, but does not move. What could be the reason for the
block not to move? What value must be overcome for it to move?
Static friction. To move it must overcome the Maximum Coefficient of Static Friction
4. For an object to remain at constant velocity,
a. it must move in an orbit. To move in orbit you must have constant acceleration
b. there must be no friction acting upon it. An object with no friction can experience
EITHER constant velocity and constant acceleration. So this is false.
c. the net force on it must be zero. (This is right.)
d. a constant force must act on it. A constant force can keep you in constant velocity, but
a constant force can also decrease your velocity.
5. A person applies a certain value of force to object A which weighs 100kg. Then he applies the
same amount of force to object B which weighs 50kg. Which object would have a greater
acceleration? Using the relationship a = F/m, Object B has a smaller m than object A. Therefore
using the inversely proportional method, Object B accelerates more.
6. A rock is dropped straight down, and when it hits the ground it exerts a force of 735N. What is the
rock’s mass? (in metric units)\. Gravity is in affect. m = F/a = 735N/9.8m/s2 = 75kg
7. A car is going around a bend at 10m/s, which has a radius of 30m. If the car weighs 500kg, what is
the centripetal force exerted? F = mv2/r = (500kg)(10m/s)2/(30m) = 1666.67N
8. A shotgun is able to fire a bullet and dispose its empty shell simultaneously. If the gun was fired at
2m above ground, and the bullet traveled 30m at the speed of 896m/s. Ignoring air resistance, would
the:
a) bullet hit the ground before the shell?
b) shell hit the ground before the bullet?
c) both the bullet and the shell would hit the ground at the same time? Gravity affects both
bullet and shell equally, since it is the only VERTICAL force acting upon the two.
d) bullet be traveling too fast to determine accurately when it will hit the ground?
9. a) At what point in our Moon’s orbit around the Earth, and our Earth’s orbit around the Sun,
produce maximum tidal waves? When they all align on the same plane.Bonus: What body of water
experiences the most drastic change in tides?Bay of Fundy (in Nova Scotia CANADA!!!)
b) In regards to the Moon and the Earth, which points on the earth would have the greatest
gravitational effect on the Moon?
i) A point closest to the moon, which is on the surface of the Earth closest to the moon.
ii) A point lying in the center of the Earth.
iii) A point furthest away from the moon, lying on the surface of the Earth.
Chapter 3
1. A car goes from 10m/s to 34m/s in 4s. If the car weighs 500kg, how much work has it done?
Solve for acceleration first: a = (34m/s-10m/s)/(4s) = 6m/s2. then solve for distance:
d=½(6m/s2)(4s)2 = 48m. Work = mad = (500kg)(6m/s2)(48m) = 144000J
2. A 1200kg Shelby going at 72m/s, crashes into a BMW that has a mass of 1600kg which bounces
it forward leaving the Shelby at rest. Note: I forgot to mention the BMW started off @ Rest.
So m2v2 = 0. How fast did the BMW end up going after the collision?
Using Law of Conservation of Linear Momentum: (1200kg)(72m/s) = (1600kg)(v2), v2=54m/s
3. What would be the new velocity if the car in the above problem hit the second car and hooked
onto each other?
Same law: (1200kg)(72m/s) = (2800kg)(v3), v3 = 30.86m/s
4. A 600g (0.6kg) basketball is launched towards the net but the player misses and only manages to
hit the backboard. Its speed was 5m/s, and the impact time between the ball and the board was
9ms (0.009s). What is the force exerted by the ball onto the board? This may have not been
covered in Ashis’s class.
F = mv/t = (0.6kg)(5m/s)/(0.009s) = 333.33N
5. An old pirate ship is 2km below ground level sitting at the bottom of the sea. Would its potential
energy be:
a. positive relative to the ground.
b. zero relative to the ground.
c. negative relative to the ground.
d. …Not enough information provided to complete the problem.
6. A person running would be going four times faster than a person walking. These two individuals
have the same mass. The person running would have:
a. the same kinetic energy as the person walking, since kinetic energy is not dependent on
speed or velocity.
b. double the kinetic energy than the person walking.
c. four times the kinetic energy than the person walking.
d. sixteen times the kinetic energy than the person walking. Velocity is Squared.
7. A person is carrying a 5kg bucket of water 1m above the ground, and walks 10m across a room
traveling at 3m/s2. What is the work done on the box? NO WORK. The direction of which the
box is traveling (it’s force) is perpendicular to the force of gravity. No work is done then.
8. An eagle hovering 150m above ground level drops its 10kg wallet (full of cash and coins). How
fast would the wallet be traveling right before it hits the ground?
Mass is not needed to solve this problem. v = √(2gd) = √(2x9.8m/s2x150m) = 54.22m/s
9. In an open system, where energy can be expelled in various forms, a 20kg object traveling at
15m/s hits a 10kg object at rest. The two objects combine to form one, of which is now traveling
at 10m/s. What is the kinetic energy lost in this inelastic collision? Name the various forms of
which this energy can be lost in. KE = ½mv2, KE1 = ½(20kg)(15m/s)2 = 2250J. KE2 =
½(30kg)(10m/s)2 = 1500J. (Note, COMBINED masses = 30kg). Difference of KE = KE2 –
KE1 = 1500J-2250J = -750J (Negative means Energy is lost). Energy could be lost in sound,
light, heat, and compression of metal.
10. An 18kg bowling ball is rolled up a hill at 7m/s starting at ground level. What is the kinetic
energy and how high does the ball roll before coming to a stop? KE = ½(18kg)(7m/s)2 = 441J
v = √(2gd), d = v2/2g = (7m/s)2/(2x9.8m/s2) = 2.5m
11. In 16s, a 100kg amateur rocket travels 1000m accelerating at 4m/s2. What is the power output by
this rocket?
Power = Work/time = (100kgx4m/s2x1000m)/(16s) = 25000J/s or Power = 25000 W (watts)