Download 2nd 6-Weeks Test Review ANSWERS

2nd Six Weeks Test Review
1.
A runner travels 40 m eastward and then 25 m northward. What is the magnitude of the runner’s displacement,
relative to its original position?
402 + 252 = c2
√2225 = 47.2 m NE
1600 + 626 = 2225
2.
A quarterback takes the football and runs backward (perpendicular to the lines on the field) for 40 m. He then runs
sideways (parallel to the lines on the field) for 15 m. The ball is thrown forward (perpendicular to the lines on the field) 60
m. When the receiver catches the football, how far is the football from its original position?
(-40 + 60 = 20)
400 + 225 = 625
202 + 152 = c2
√625 = 25 m
3.
Johnny rides his skateboard westward down the street where he sees Jose standing on a curb. From the Johnny’s
perspective, describe Jose’s motion.
Jose will appear to travel eastward
4.
List the Units for the following quantities:
a.
Distance:
m
b.
Velocity:
m/s
c.
Acceleration:
m/s2
d.
Force (2 forms of units):
e.
Mass:
kg
f.
Time:
s
N = kg∙m/s2
5.
Draw a position vs time graph that shows acceleration and draw a tangent line to the curve. What does the slope
of the tangent line represent?
Slope of the line represents the speed of the object
6.
The figure to the right shows the path of a projectile. Label the
horizontal and vertical velocities with vectors.
7.
A horse trots a distance of 105 meters in 15 seconds. What is
the average velocity of the horse?
𝑣=
8.
𝑑
𝑡
105 𝑚
15 𝑠
= 7 m/s
What is the definition of acceleration?
Rate of change of velocity
9.
Describe the motion of a car with a positive velocity and negative acceleration.
Car is moving forward and slowing down
10.
If you know a car’s acceleration (magnitude and direction), what other information would you need to determine
if the car’s speed is increasing or decreasing?
Nothing, positive and negative acceleration show increase and decrease
11.
A bowling ball and a feather are dropped from rest in a vacuum, which will reach the ground first?
Will reach ground at same time
12.
If your lab partner holds a ruler between your finger and thumb and releases it from rest, how far can you expect
the ruler to fall before you catch it? (Disregard air resistance. (a = g = 9.8 m/s2)
(Need to know reaction time)
𝑑 =
1
𝑎 𝑡2
2 𝑔
13.
A model rocket flies horizontally off the edge of a cliff at a velocity of 75.0 m/s. If the canyon below is 250.0 m
deep, how far from the edge of the cliff does the model rocket land? (ay = g = 9.8 m/s2)
2𝑑
𝑡= √
𝑎
𝑔
2(250 𝑚)
√ 9.8 𝑚/𝑠2 = 7.14 s
14.
𝑑ℎ = 𝑣ℎ 𝑡
(75 m/s)(7.14s) = 535 m
What is the definition of force? Is force a vector or scalar quantity?
Push or pull exerted on an object, vector quantity
15.
How do you represent the magnitude of a vector?
Magnitude shown by length of vector
16.
What does the word “net” mean in physics?
Total sum
17.
18.
19.
List Newton’s Three Laws:
1st:
Law of Inertia – Objects in motion stay in motion and objects at rest stay at rest until acted on by an
outside force
2nd:
F = ma – Objects acceleration is directly proportional to the force applied and indirectly proportional to
the mass of the object
3rd:
Action – Reaction Pairs – When an object exerts a force on another object, an equal but opposite in
direction force is applied back
Provide an example of each of Newton’s Laws:
1st:
Book on a table will remain until picked up or pushed; Bowling ball will roll until friction or wall stops it
2nd:
Heavier objects take more force to accelerate than lighter objects.
3rd:
Mr. Huynh ran in to Coach Smith in the hallway and ended up falling backwards after bouncing off
What is the definition of inertia?
Ability of an object to resist a change in motion
20. What are the four basic forces that we show on free body diagrams?
Gravity, Normal, Applied, Friction
Use the figure below to answer Questions 21-22
21.
In the free body diagrams above, identify the net force and label the four forces:
Figure (1): Net: ___5N____
Figure (2): Net: ____0____
FN: _______
FN: ___2N____
Fg: ___5N____
Fg: ___2N____
FA: ___5N____
FA: ___5N____
Ff: ___5N____
Ff: ___5N____
Figure (3): Net: ___3N_____
22.
Figure (4): Net: __2N___2N___
FN: ___2N____
FN: _______
Fg: ___5N____
Fg: ___2N____
FA: ___2N____
FA: ___3N____
Ff: ___2N____
Ff: ___5N____
In the free-body diagram above, identify the motion of the box in each figure.
23.
A turtle on a skateboard ties a rocket to his shell in order to get a “push.” The total mass of the turtle, skateboard,
and rocket is 82 kg. Calculate the force of the rocket if his acceleration is 1.60 m/s2. What force is being applied?
F = ma
24.
What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sec2?
F = ma
25.
(1000 kg)(-9.8 m/s2) = -9800 N
What is the acceleration of a 50 kg object pushed with a force of 500 newtons?
𝑎=
26.
(82 kg)(1.6 m/s2) = 131.2 N
𝐹
𝑚
500 𝑁
50 𝑘𝑔
= 10 m/s2
The mass of a large car is 1000 kg. How much force would be required to accelerate the car at a rate of 3
m/sec2?
F = ma
27.
A 50 kg skater pushed by a friend accelerates 5 m/sec2. How much force did the friend apply?
F = ma
28.
(1000 kg)(3 m/s2) = 3000 N
(50 kg)(5 m/s2) = 250 N
A force of 250 N is applied to an object that accelerates at a rate of 5 m/sec2. What is the mass of the object?
𝑚=
𝐹
𝑎
250 𝑁
5 𝑚/𝑠2
= 50 kg
29.
List the action-reaction force pair for each set of items:
a.
Hammer and Nail
Hammer hits the nail, nail supplies force back causing hammer to bounce off
b.
Baseball and Bat
Baseball thrown and contacts bat, bat supplies force back causing ball to reverse direction
c.
Head and Soccer Ball
Soccer ball flies through air and hits person’s head, head pushes back causing ball to bounce off