Final exam review help?!?!

- anonymous

Final exam review help?!?!

- schrodinger

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- anonymous

I have 3 study sheets.

- anonymous

##### 1 Attachment

- anonymous

for # 1 i got 34km/h

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## More answers

- anonymous

no, you have to multiply by 3.6

- anonymous

why?

- anonymous

|dw:1383926098747:dw|

- anonymous

4.9 m change it to km it is 0.0049km/s * 60 *60 = 33.8

- anonymous

4.9 m change it to km it is 0.0049km
this is correct.
but then when you change seconds into hours you divide by 3600
since you divide it in the denominator it is like multiplying by 3600
so eventually
0.0049 * 3600 = 17.64 km/h

- anonymous

look at my draw

- anonymous

-> 0.0049km/s * 60 *60 = 33.8
it is 17.64 and not 33.8

- anonymous

0.0049 * 60 * 60 = 17.64

- anonymous

maybe you did mistake when you enter the numbers into the calculator

- anonymous

the options are 94,000 km/h
34 km/h
2.6 km/h
34,000,000 km/h

- anonymous

well what can i say :
http://www.unitconversion.org/velocity/meters-per-second-to-kilometers-per-hour-conversion.html
you may check yourself here

- anonymous

0.0049 * 60 * 60 = 17.64
do it in the calculator and see

- anonymous

m is for meters right ? :O

- anonymous

yes. Idk maybe the options are wrong. i keep getting 17.64 too.

- anonymous

i guess they are wrong

- anonymous

A physical quantity X depends on mass, distance, and time. Use dimensional analysis to decide which of these is a possible expression for X where a is acceleration, v is velocity, and F is force.
It's either X=Ft or X=1/2at^2 right?

- anonymous

well in x=1/2at^2 there is no mass

- anonymous

would X=Ft work?

- anonymous

you have options ?

- anonymous

yes
X=Ft
X=at
X=vt
and X=1/2at^2

- anonymous

yes Ft is the one

- anonymous

for 3 I want to say B?

- anonymous

no

- anonymous

(just to make sure that you understand
Ft units are [kg m / s] so it has mass distance and time)

- anonymous

now for 3. think what happens to y when x is small
and when x is big..

- anonymous

im confused

- anonymous

y = k/x
for low values of x like when x goes to zero
y will be very large
for high values of x like when x goes to infinity
y will be very low
agree ?

- anonymous

yes so thus my answer is A? AS X gets larger Y gets smaller.

- anonymous

yes ! A

- anonymous

A balloon is expanded to the same volume as that of a human head. Do an order-of-magnitude estimate of the volume of this balloon in cm3

- anonymous

1,000 cm3?

- anonymous

i think it iscorrect

- anonymous

Which equation represents inverse proportionality?
y=mx?

- anonymous

y=mx is linear proportionality direct ..

- anonymous

y=mx
y=mx^2 +b for nonzero b
y=m/x
y=mx^2

- anonymous

we had one like this before ..
we want inverse
so when one is high the other is low
and when one is low the other is high ...

- anonymous

so how would that be represented by an equation?

- anonymous

y=m/x
as i said we had something like this before
when we chose graph A

- anonymous

oh. okay so its like the graph.

- anonymous

A bicycle and rider travel along a road. Which of the following statements is true?

- anonymous

The bicycle wheels rotate and translate the entire bike and the rider.

- anonymous

please write the other options as well

- anonymous

Only the bicycle rider undergoes a translation.
The bicycle wheels rotate and translate the entire bike and the rider.
Only the bicycle undergoes a translation.
Neither the bicycle nor the rider undergoes a translation.

- anonymous

so your answer is correct

- anonymous

Suppose you are on a conveyor belt walkway at an airport. The walkway is moving at 0.50 m/s. You walk backward at 0.80 m/s to hand your suitcase to a friend who is 3.0 m behind you. A security guard stands alongside the walkway watching this. What is your speed relative to the guard? im not sure how to do this one.

- anonymous

so if you were not moving
the relative speed was 0.5m/s
correct?

- anonymous

correct

- anonymous

now i guess the 0.8m/s walking backwards is relative to the belt!
so we have:
0.5 - 0.8

- anonymous

do you understand why ?

- anonymous

because he is walking backwards at 0.8

- anonymous

yes.
not moving on the belt :
0.5
moving forward on the belt at x :
0.5 + x
moving backward on the belt at x:
0.5 -x

- anonymous

okay

- anonymous

An airplane travels southwest a distance of 650 km at a velocity of 430 km/h. How long does the trip take in hours? 1.5?

- anonymous

correct

- anonymous

(650/430 = 1.5116...)

- anonymous

On the position-time graph, what is the average velocity between 5 s and 10 s?

- anonymous

##### 1 Attachment

- anonymous

not sure about this one.

- anonymous

average velocity = (y2-y1) / (t2 -t1)

- anonymous

between two points : (t1,y1) and (t2,y2)

- anonymous

4m/s?

- anonymous

at 5 sec the height is 10 so (5,10)
and at 10 sec the height is 30 so (10,30)
(30-10) / (10-5) = 4
correct

- anonymous

A ball is dropped from a tower. It strikes the ground with a speed of +19.0 m/s. How high is the tower?
18.4m

- anonymous

you take the value of g as 9.8 ?

- anonymous

so yes correct..

- anonymous

v=gt
so
t=v/g
now plug it into
h = 0.5gt^2 = 0.5v^2/g = 18.4

- anonymous

A ship travels south at 15 km/h for 4 h. What is the ship's displacement in km? 60km South?

- anonymous

correct
15*4 = 60

- anonymous

A ball is rolling down a hill at +2.0 m/s. The ball is uniformly accelerating at +4.0 m/s2. What will the ball's velocity be 3.0 s later? 14m/s because v=u+at

- anonymous

What additional force must be applied so that the block does not accelerate?
10N West?

##### 1 Attachment

- anonymous

A 1,560 kg car is accelerating at 1.30 m/s2. What net force acts on the car?
F=ma so 2028 rounds to 2030?

- anonymous

Which statement is equivalent to Newton's first law?
No net force acting on an object means no acceleration.

- anonymous

A tension force of 2.50 N acts horizontally on a 2.00 kg block. The block accelerates at 0.750 m/s2. What is the force of kinetic friction?
1N?

- anonymous

however the options are
- 3.33 N
- 1.50 N
- 1.00 N
- 4.00 N

- anonymous

ball - correct
block - correct
car - correct
newtons first law - seems like it is correct but it is better to see the other options
tension - it is -1 (remember that the kinetic friction force is against the direction of the motion) so you right about the magnitude but the sign is there to show what is the direction.

- anonymous

i guess that you solved it like
2.5 - Fk = ma
and then you got Fk =1
but look at the equation - you already chose the direction with the minus sign.

- anonymous

No net force acting on an object means no acceleration.
For every action there is an equal and opposite reaction.
Mass is directly proportional to weight.
The acceleration of an object is the net force acting on it divided by its mass.

- anonymous

so it is right.

- anonymous

The acceleration due to gravity on the surface of Mars is gmars = 3.7 m/s2. How much would an 11 kg bag of potatoes weigh on Mars? 41N?

- anonymous

yes

- anonymous

3.7*11

- anonymous

The 48 kg student on skates pushes the 40 kg student on skates. The 40 kg student accelerates at 3.0 m/s2. What is the acceleration of the 48 kg student?

##### 1 Attachment

- anonymous

im not sure about this one

- anonymous

newton's third law..

- anonymous

another hint ?

- anonymous

F=ma?

- anonymous

newton's third says that if body A push body B with force F
then body B push body A with the same force F in the opposite direction

- anonymous

i feel stupid. sorry. ive been up all night

- anonymous

what is the force that acts on the 40kg student ?

- anonymous

dont feel stupid your answers are good

- anonymous

3m/s?

- anonymous

i asked about the force
The 40 kg student accelerates at 3.0 m/s2
so the force on him is
40 * 3 = 120 N
now according to newton's third law it is the force that acts on the second student as well (in the other direction)
so
120 = 48 * a
a = 120 / 48

- anonymous

2.5 m/s

- anonymous

yes (well they might have there -2.5 since it is in the other direction)

- anonymous

A 0.156 kg ice puck collides with a 0.170 kg ice puck. Both were originally moving at the same speed. Which one has the larger change in velocity?

- anonymous

The 0.156 kg puck changes velocity the most.
The 0.170 kg puck changes velocity the most.
They both have the same change in velocity.
They each have no change in velocity.
I say it is the first one...

- anonymous

so the situation is that they are moving toward each other ? and then elastic collision ?

- anonymous

i asume

- anonymous

correct then

- anonymous

A diver jumps down on a springboard, bounces back up, and dives into the pool. Which of these is one of the action-reaction pairs involved?

- anonymous

the force on the board as the diver bends it downward and the force on the diver as the board springs back up
the force of the board on the diver as he moves down and the force of the board on the diver when pushed back up
the springiness of the board in moving back up
the force the diver exerts on the water and the force the water exerts on the diver

- anonymous

so what do you think ?

- anonymous

A?

- anonymous

yes

- anonymous

newton's third law always involved two bodies

- anonymous

A force of 100 N acts in a direction at an angle of 30Â° with the x-axis. What is the magnitude of the x component of the force?

- anonymous

about 90N?

- rajat97

|dw:1383940674800:dw|
yes the accurate answer is 86.5 newton

- anonymous

Two movers are pushing a large crate along the ground, one with a force of 30 N east and the other with a force of 40 N north. The crate does not move. What is the magnitude of the force of static friction?

- rajat97

always remember for ease of resolving the forces into perpendicular directions, the component of force near the angle is the force x cos theta and the one which is away from it is f x sin theta

- rajat97

|dw:1383940923978:dw|
the forces are perpendicular so the resultant is \[\sqrt{F1^{2}+F2^{2}}\]
therefore the resultant is 50N and the force of friction is equal to it

- anonymous

Which of these is true about an object thrown straight up in the absence of air resistance?

- anonymous

Its acceleration is constant.
The direction of its velocity is constant.
Its acceleration and velocity are both momentarily zero at maximum height.
Its acceleration increases as it falls.

- anonymous

so what do you think ?

- anonymous

C?

- anonymous

well no does g change during the motion ?

- anonymous

i want to say no

- anonymous

because the acceleration does not change

- anonymous

so it would be A?

- anonymous

yes

- anonymous

note that at the maximum height the velocity is indeed zero.
but what makes it go down ? the acceleration.

- anonymous

The velocity of an object increases from 5.0 m/s to 15 m/s in 2.0 s. What is the average acceleration of the object?

- anonymous

5m/sn2

- anonymous

ok

- rajat97

i'm on it
average velocity is change in velocity in unit time
so here it is 15-5/2 =5m/s^2

- anonymous

is it + or -?

- rajat97

change in velocity is final velocity -initial vel
as final vel is greater than initial vel , it will be posotive

- rajat97

and if vel is increasing, then acceleration is +ve

- anonymous

What shape does a position vs. time graph have for an object in uniform acceleration?

- anonymous

cubic
inverse
quadratic
linear

- rajat97

i think its cubic as the degree of the equation increases as we move towards position time graph
i mean to say
its linear in v-t graph
so it may be quadratic in x-t graph

- anonymous

hi again

- anonymous

okay and hi

- rajat97

are your questions finished

- anonymous

ok.bye

- rajat97

please inform me when your questions are finished

- rajat97

somethings gotta go wrong with openstudy well i live in india and its 2:45 am and i think i shall sleep now but if you have any questions please post them i'm onine for 15 mins

- anonymous

no, my mom needed help with something.

- anonymous

A book is being pushed along a table at constant speed. The coefficient of static friction is 0.75, and the coefficient of kinetic friction is 0.30. The book has a mass of 0.50 kg. What is the force of friction?

- anonymous

1.5N

- anonymous

correct

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