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pychu [463]
3 years ago
5

Two ice boats (one of mass m, one of mass 2m) hold a race on a frictionless, horizontal, frozen lake. Bath ice boats start at re

st, and the wind exerts the same constant force on both iceboats. After moving a same distance s, which iceboat crosses the finish line with a quicker speed v
Physics
1 answer:
Elenna [48]3 years ago
5 0

Answer:

They both cross the finish line with the same kinetic energy

Explanation:

Same force, same displacement, so same KE at the location of the finish line. They don’t cross the line at the same time, but that was not the question!

∆KA= (mA/2)vF,A2

∆KA=∆KBso vF,B/vF,A= (MA/MB)1/2∆KB= (mB/2)vF,B2

Lighter boat goes faster so reaches finish line 1st

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On a clear day at a certain location, a 119-V/m vertical electric field exists near the Earth's surface. At the same place, the
IrinaVladis [17]

Answer:

(a) 62.69 nJ/m^3

(b) 1015.22 μJ/m^3

Explanation:

Electric field, E = 119 V/m

Magnetic field, B = 5.050 x 10^-5 T

(a) Energy density of electric field = \frac{1}{2}\varepsilon _{0}E^{2}

          =\frac{1}{2}\times 8.854\times 10^{-12}\times 119\times 119

          = 6.269 x 10^-8 J/m^3 = 62.69 nJ/m^3

(b) energy density of magnetic field = \frac{B^{2}}{2\mu _{0}}

=\frac{\left ( 5.05\times 10^{-5} \right )^{2}}{2\times 4\times 3.14\times 10^{-7}}

= 1.01522 x 10^-3 J/m^3 = 1015.22 μJ/m^3

8 0
3 years ago
A ball is dropped from an upper floor, some unknown distance above your apartment. As you look out of your window, which is 1.50
laila [671]

Answer:

The ball is dropped at a height of 9.71 m above the top of the window.

Explanation:

<u>Given:</u>

  • Height of the window=1.5 m
  • Time taken by ball to cover the window height=0.15

Now using equation of motion in one dimension we have

s=ut+\dfrac{at^2}{2}

Let u be the velocity of the ball when it reaches the top of the window

then

1.5=0.15u+\dfrac{9.8\times0.15^2}{2}\\u=3.96\ \rm m/s\\

Now u is the final velocity of the ball with respect to the top of the building

so let t be the time taken for it to reach the top of the window with this velocity

3.96=gt\\t=0.4\ \rm s\\

Let h be the height above the top of the window

h=\dfrac{gt^2}{2}\\\\h=\dfrac{9.8\times 0.4^2}{2}\\h=9.71\ \rm m

3 0
3 years ago
a horse moves a sleigh 1.00 kilometers by applying a horizontal 2000 Newton force on its harness for 45 minutes. what is the pow
tatyana61 [14]
--  If 2,000 newtons of force were applied through a distance of 1,000 meters,
then 2,000,000 newton-meters = 2,000,000 joules of work were done.

-- 45 minutes = (45 x 60) = 2,700 seconds

-- Power = (work) / (time) = (2,000,000 j) / (2,700 s) = <u>740.74 watts</u>

Interestingly, that's almost exactly 1 horsepower.  (0.99295... of 746 watts)
8 0
3 years ago
Which best describes a concave lens?
-Dominant- [34]

Answer:

Explanation:

Concave lens also called as diverging lens i.e. it diverges ray of light coming towards it.

Concave lens is thicker at the edges and thinner at the center.

Concave lens formed the virtual image of the object i.e. it cannot be trace on screen. This lens is used to treat the nearsightedness or myopia in which a person is unable to see the far object clearly.

4 0
3 years ago
Timmy bikes to school 3 kilometers east and 2 kilometers south. What is Timmy's final displacement?
vovikov84 [41]

Answer:

3.6km South East

Explanation:

Displacement is the shortest distance between the starting point and the ending point and the direction it is displaced in. To calculate the displacement we can use the pythagoras theorem because the 3km East and the 2km south form the two shorter sides of a right angled triangle between the starting and ending points. So, the displacement is the length C of the triangle which we can calculate as follows:

Pythagoras Theorem:

a^2+b^2=c^2

(2)^2+(3)^2=c^(2)

4+9=c^2

Square root 13 = c

c=3.6km (1dp)

The total displacement is 3.6km and is in the approximate direction of South East (because he travelled east and south).

Hope this helped!

8 0
3 years ago
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