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olga55 [171]
3 years ago
13

A 40 kg-skier starts at the top of a 12-meter high slope. At the bottom, she is traveling 10 m/s. How much energy does she lose

to friction? A.She doesn't lose any because mechanical energy is always conserved.
B.4,704 J
C. 2,000 J
D.2,704 J
Physics
2 answers:
julia-pushkina [17]3 years ago
8 0

2704 j is my answer i did the math. good luck

Ad libitum [116K]3 years ago
8 0

Answer : Lost energy, E = 2704 J

Explanation :

Given that,

Mass of the skier, m = 40 kg

Height from bottom, h = 12 m

Velocity at the bottom, v = 10 m/s

At the top she will have potential energy and at the bottom she will have kinetic energy. Finding one by one :

Potential energy, P = m g h

P = 40 kg × 9.8 m/s² × 12 m

P = 4704 J

Kinetic energy, K = 0.5 × m v²

K = 0.5 × 40 kg × (10 m/s)²

K = 2000 J

Lost energy, E = P - K

E = 4704 J - 2000 J

E = 2704 J

The energy that is lost to friction is 2704 J.

So, the correct option is (D) " 2704 J "

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The speed of a electron that is accelerated from rest through an electric potential difference of 120 V  is 6.49\times10^6m/s

<h3>How to calculate the speed of the electron?</h3>

We know, that the  energy of the system is always conserved.

Using the Law of Conservation of energy,

\triangle K+\triangle U=0

Here, K is the kinetic energy and U is the potential energy.

Now, substituting the formula of U and K, we get:

(\frac{1}{2} mv^2)+(-q\triangle V) =0------(1)

Here,

m is the mass of the electron

v is the speed of the electron

q is the charge on the electron

V is the potential difference

Let v_f and v_i represent the final and initial speed.

Here, v_i =0

Solving for v_f, we get:

v_f=\sqrt{\frac{-2q\triangle V}{m} }

=\sqrt{\frac{2\times1.602\times10^{-19}\times 120}{9.109\times10^{-31}} }

=6.49\times10^6m/s

To learn more about the conservation of energy, refer to:

brainly.com/question/2137260

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4 0
1 year ago
Why is the unit of momentum called derived unit​
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Answer:

the SI unit of momentum is :- kg.ms-1

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E=p2/2m

p=(2Em)1/2

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Explanation:

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3 years ago
1. What is the average speed of a runner that<br> travels 100 meters in 9.7 seconds?
alexdok [17]

Answer:

10.30928 m/s

Explanation:

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atroni [7]

Answer:

Displacement from the starting position is 103.21m

Explanation:

If you draw these directions, it will create the two legs of a triangle.

Using this method, you can visualize why your displacement is what it is.

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{a}^{2}  +  {b}^{2}  =  {c}^{2}

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