1. Sebuah bkubus dengan beban 100 gr di atasnya mengapung di air. Jika beban disingkirkan kubus naik setinggi 2 cm. Berapakah volume kubus?

2. Seorang anak berlari di atas geladak kapal sepanjang 180 m dengan kecepatan 2 m/s (searah gerak kapal) relatif terhadap kapal. Jika kapal bergerak dengan kecepatan 4 m/s di atas es tanpa gesekan, hitung jarak yg ditempuh kapal saat anak tiba di ujung kapal. ( massa anak 40 kg massa kapal 800 kg)


Jawaban:

Keyword: Pembahsan soal fisika, gaya archimides, buoyancy, gaya apung, gerak lurus

Electrostatic Net Force?

Three charges, Q1, Q2, and Q3 are located in a straight line. The position of Q2 is 0.235 m to the right of Q1. Q3 is located 0.147 m to the right of Q2. 

a) In the above problem, Q1= 1.73·10-6 C, Q2= -3.22·10-6 C, and Q3= 3.33·10-6 C. Calculate the total force on Q2. Give with the plus sign for a force directed to the right. 

b) Now the charges Q1= 1.73·10-6 C and Q2= -3.22·10-6 C are fixed at their positions, distance 0.235 m apart, and the charge Q3= 3.33·10-6 C is moved along the straight line. For what position of Q3 relative to Q1 is the net force on Q3 due to Q1 and Q2 zero? Use the plus sign for Q3 to the right of Q1.

Answer:

Cermin cekung

If an 3cm high image is located 36cm in front of the concave mirror with a focal length of 5cm, what is di(distance of the image from the mirror), hi(height of image), and Magnification of the image?

 

Answer

 

Gerak lurus berubah beraturan kasus peluru pesawat

An airplane is flying with a velocity of 242 m/s at an angle of 30.0° with the horizontal, as the drawing shows. When the altitude of the plane is 2.3 km, a flare is released from the plane. The flare hits the target on the ground. What is the angle θ? 

Picture of problem : http://www.webassign.net/CJ/03-37alt.gif

Answer:

GLBB pertemuan dua bola secara vertikal

From the foot of a tower 90m high, a stone is thrown up so as to reach the top of the tower. Two second later another stone is dropped from the top of the tower. The two stones will meet at

Answer:

Calculate the velocity of the joint mass.?

A mass of 120kg moves along a straight line at 7m/s. It collides with another mass of 175kg moving in the opposite direction at 4m/s on the same straight line. The two masses join together on collision; calculate the velocity of the joint mass.

some working out would be good as well

Answer:

 you can use momentum law:

m1*v1 + m2*v2 = m1*v1' + m2*v2'

because they join together, velocity is same, thus

m1*v1 + m2*v2 = m1*v'+m2*v'
m1*v1 + m2*v2 = (m1+m2)*v'
120*7+175*(-4)=(120+175)*v'
v'=0.47 m/s

so the velocity joint mass is 0.47 m/s

How do electric motor works?

electric motor uses relation between current, magnetic flux and force.
you can visit this blog for explanation about your question, there are figures to help you understand
http://simple-engineering.blogspot.com/2…

The Proper Power meter for CO2 laser?

Hi every one
In my experiments i need to measure the power of light emitted from my Co2 Laser. What kind of power meter can be useful for my job?
can you please suggest me some laser power meters?

thanks alot

Answer:

Actually, it depends on class of laser you will measure and in what is the range of laser wavelength.
I have experience measuring laser power, I used LabMax-Top, it is coherent product.
I think you can also use that instrument.

Difference between engine and motor?

very different..
engine use heat energy (can be from kerosene, gasoline, etc) to produce rotation (kinetic energy)
example: car engine

motor use electrical energy to produce rotation, example : fan

Engineering Physics or Mechanical Engineering?

I live in Colombia but I plan to go to college in the USA, either in New York or California. The thing is I love physics and I'm really good at it, also math. I don't really know if I should study engineering physics or mechanical engineering....many people say mechanical engineering is mostly for men... which would you recommend me? what jobs can I get if I study EP or ME, also which one is easier to find a job in and which one is better paid? what are the pros and cons of both of them?

Pleaseee help me figure it out :D

My Answer:

In Engineering physics, you will learn almost all fundamental of engineering, such as thermodynamics, electronics, materials, instrumentation, optic, acoustic,etc. So if you choose Engineering Physics you will get wider knowledge about engineering. but not deep. This is can be advantages and disadvantages.

If you choose mechanical engineering, probably you will get deeper but not wide (focus on related with mechanical engineering)

Both of them is good and needed in many jobs

If you study EP you can get many kind of jobs, including electrical engineering job or mechanical engineering jobs.

FYI, I graduated from EP, now I work with the people who graduated from mechanical engineering.

Determining the precentage of mass in mixing two different temperature of water

How do I calculate the percentages to mix water at 1 degree to water at 250 degress to get 80 degress?

 

Answer:

you can use "black" principle:

mhot*c*(Thot-Tmix)=mcold*c*(Tmix-Tcold)

where:
mhot: mass of water 250 degrees
mcold: mass of water 1 degrees
Thot: 250 degrees
Tcold: 1 degrees
c: heat specific

because all of them is water, so they have same heat specific, then:

mhot*c*(250-80)=mcold*c*(80-1)

mhot/mcold = (250-80)/(80-1)=2.15

it means to get 80 degrees, the ratio of hot and cold water is 2.15.
if you have mhot 2.15kg, then you need 1 kg mcold

so the percentage of hot water: 2.15/(2.15+1)*100%=68.25%
and percentage of cold water : 1/(2.15+1)*100%=31.75%

Finding the strength of electric field between two charges

Electric Field problem? Please help?

Point P lies in between charges A and B. A has a charge of 30, and B has a charge of 10. P is .2m away from A, and .5m away from B. Determine the electric field strength at point P

Answer:

Let us say the position is like this:

A P B


electric field caused by A:

E=k*q/(r^2)=9*10^9 * 30 / (2^2)= 6.75*10^10 N/C (direction is to the right)

electric field caused by B:
E=k*q/(r^2)=9*10^9 * 10 / (5^2) =3.6*10^9 N/C (direction is to the left)

So, the total electric field at P is:
6.75*10^10 - 3.6*10^9= 6.39*10^10 N/C (the direction is to the right)

Determining the gravity acceleration at distant point from earth

A space shuttle is in orbit 400 km from the Earth's surface, and circles the Earth about once every 90 minutes.Find the centripetal acceleration of the space shuttle in its orbit (Earth radius = 6.38 x 10^3 km)
I got the answer 5350 m/s^2 (forgot to factor in the radius of the earth). Then I got the answer 155 m/s^2 (remembered to factor in the radius of the earth)
Apparently the real answer is 0.9g's = 0.9 x 9.8 = 8.82 m/s^2

Now I'm following the steps in my book to the decimal point and I still don't seem to know how they got that answer.
Could someone show me the proper equation?

this is the solution:
to make it easy, we have to calculate at the same system unit.

radius of the space shuttle: 400 km + 6380 km = 6780 km
it circles the earth every 90 minutes (5400 second).
The distance in once circle is = 2*pi*Radius=2*3.14*6780=42578.4 km = 42578400 m
from this we can obtain the velocity of shuttle: distance/time = 42578400/5400= 7884.8 m/s

The centripetal acceleration is = velocity^2/Radius= (7884.8^2)/6780000= 9.16 m/s^2
as we know the g = 9.8 m/s^2, 
so the answer is 9.16/9.8 = 0.93 g

Two vehicles meet with different start and velocity

A bus has traveled 210 miles, and continues at a rate of 50 miles per hour. A van has driven 170 miles, and continues at a rate of 60 miles per hour. In how many hours will the two vehicles have traveled the same distance?

let us say:
S1: the distance of bus
S2: the distance of van
t: the time when the vehicles have the same distance

in this problem we are asked to determine how many hours the vehicle will have the same distance, so:

S1=S2 .......(1)

S1= 210 + (50*t) ....(2)
S2=170+(60*t) ...........(3) 

because S1=S2, then: 

210 + (50*t) = 170+(60*t)
210-170 = (60*t)-(50*t)
40=10*t
thus we can get the t =4

the answer is 4 hours

Derivaion to determine the potential energy of spring

The formula for the potential energy stored in a spring is given by Us= (1/2)k(x)^2. Explain the 1/2 in the equation using the fact that W=FxD (note: F= average force over d). Any help would be greatly appreciated! Thanks!

Maximum efficiency estimation of power plant

Using the theoretical thermodynamic maximum efficiency for a Carnot cycle operating between an average outdoor temperature of 27oC and a maximum steam temperature for a PWR nuclear plant of 3150C, estimate the maximum efficiency of the nuclear plant as a heat engine. Typical operating efficiencies are about 30-35%.

Force of circular moving object

Physics: energy conservation?

A small block with mass 0.0450 slides in a vertical circle of radius 0.0730 on the inside of a circular track. There is no friction between the track and the block. At the bottom of the block's path, the normal force the track exerts on the block has magnitude 3.55 
What is the magnitude of the normal force that the track exerts on the block when it is at the top of its path?

Menhitung koefisien muai zat

pada suhu 20 derajat celcius, sebuah botol bisa menampung 300 g zat cair sedangkan pada suhu 60 derajat celcius hny mampu menampung 298,2 g zat cair yg sma. hitung koef muai vol zat cair jka koef muai btol 6*1o pangkat -6.makasih bantuannya

Katrol pejal tunggal dengan dua massa

DIKETAHUI : m1=1 kg m2= 2 kg, massa katrol mk=2 kg. katrol terbentuk silinder pejal dengan jari-jari R. percepatan gravitasi bumi g=10m/s^2. percepatan sistem adalah..?

yang mau bantu tolong tulis caranya ya...?:)

Penentuan daya kalor heater

Air sebanyak 5000 cc di dalam panci mengalami pemanasan tetap oleh sebuah heater yang memiliki daya 1000 watt dengan efisiensi 80%. Kapasitas panas panci 1000 kal/K. Dalam 15,75 menit suhu air beserta panci meningkat dari 25C menjadi 50C. Hitung:

(a) Kalor yang dihasilkan heater

Penentuan kedalaman laut dengan sonar

Cepat rambat bunyi di air laut 1,5 km/s. Kapal A melepaskan sinyal bunyi ke dalam laut. Bunyi yang dipantulkan oleh dasar laut diterima oleh kapal B 2 detik kemudian. Jarak antara kedua kapal 1,8 km. Tentukan kedalaman laut dan selisih waktu kedua kapal menerima bunyi pantul.

Keyword: Pembahasan soal fisika, sonar, gelombang bunyi, penetuan kedalaman laut

Penentuan tititk tertinggi objek dan kecepatan jatuhnya

Sebuah benda yang massanya 500 gram dan diam di tanah, diangkat ke atas dengan gaya tetap 10 Newton selama 5 detik, kemudian dilepaskan. Titik tertinggi yang dicapai benda adalah .... dan benda akan menumbuk dengan kecepatan ...

Menentukan kerja pada proses adiabatik

1.sebanyak 2,4 mol gas oksigen pada 47 C dimampatkan melalui proses adiabatik, sehingga suhu mutlaknya meningkat menjadi tiga kali semula. berapa besar usaha yang harus diberikan pada gas O2?

Mengukur temperatur dengan hambatan listrik

Sebuah termometer hambatan logam memiliki hambatan 75 ohm sewaktu dicelupkan ke dalam es yang sedang melebur, dan memiliki hambatan 96 ohm sewaktu dicelupkan ke dalam air yang sedang mendidih. Tentukan suhu yang ditunjukkan termometer tersebut ketika hambatan logam:

a. bernilai 82 ohm
b. bernilai 72 ohm

Jawaban:

Cahaya pada kisi

Sebuah kisi yang memiliki 300 garis tiap cm kita gunakan untuk menentukan panjang gelombang cahaya. Sudut antara garis pusat dan garis pada orde I adalah 80 (sin 80 = 0,140). Dari hasil di atas,  panjang gelombang cahaya itu adalah …
A. 2,70 × 10-8 m
B. 3,70 × 10-7 m
C. 3,70 × 10-6 m
D. 4,63 × 10-8 m
E. 4,67 × 10-7 m

Menentukan hambatan listrik

Volt meter V memiliki hambatan 1 kΩ, Amperemeter A memiliki hambatan 1 Ω. Kedua alat ini digunakan untuk mengukur hambatan X dengan menggunakan rangkaian di atas. Pada V terbaca 5 volt, pada A terbaca 25 mA. Besarnya hambatan X …

A. 200 Ω
B. 250 Ω
C. 0,2 Ω
D. 0,25 Ω
E. 100 Ω

Konsumsi daya listrik lampu

Sebuah bola lampu listrik dibuat 220 V – 50 W , yang mana dari pernyataan-pernyataan berikut yang benar ?
A. dayanya selalu 50 watt
B. tegangan minimum diperlukan untuk menyalakannya adalah 220 volt
C. tahanannya adalah 484 ohm
D. diperlukan arus sebesar 5/22 ampere bila menyalakannya
E. menghabiskan energi sebesar 50 joule dalam 1 detik bila dihubungkan dengan sumber tegangan 220 volt