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dexar [7]
3 years ago
14

A 10 kg box initially at rest is pulled with a 50 N horizontal force for 4 m across a level surface. The force of friction actin

g on the box is a constant 20 N. How much work is done by the normal force pushing up on the box from the ground?
A. 10 J
B. 0 J
C. 100 J
D. 50 J
Physics
1 answer:
emmasim [6.3K]3 years ago
5 0

Answer: 0 j

Explanation:

It is given that,

Mass of the box, m = 10 kg

Force with which the box is pulled, F = 50 N

It is moved a distance of 4 m

Force of friction acting on the box, f = 20 N

We need to find the initial kinetic energy the box have. It is clear that the box is at rest initially. As there is no motion in the box at that time. The formula for the kinetic energy of the box is given by :

As v = 0

So, the initial kinetic energy of the box is 0. Hence, this is the required solution.  

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Two obiect accumulated a charge of
tamaranim1 [39]

Answer:

A. 181.24 N

Explanation:

The magnitude of hte electrostatic force between two charged objects is given by the equation

F=k\frac{q_1 q_2}{r^2}

where

k is the Coulomb's constant

q1, q2 are the magnitudes of the two charges

r is the separation between the charges

In this problem, we have:

q_1=4.5\mu C=4.5\cdot 10^{-6}C is the magnitude of the 1st charge

q_2=2.8\mu C=2.8\cdot 10^{-6}C is the magnitude of the 2nd charge

r = 2.5 cm = 0.025 m is the separation between the charges

Therefore, the magnitude of the electric force is:

F=\frac{(9\cdot 10^9)(4.5\cdot 10^{-6})(2.8\cdot 10^{-6})}{(0.025)^2}=181.44 N

So, the closest answer is

A) 181.24 N

3 0
3 years ago
An electric generator converts kinetic energy into --------<br> energy.
pickupchik [31]

The correct answer to the question is :  Electric energy

EXPLANATION :

As per the question, we have an electric generator.

Before coming into any conclusion, first we have to understand the function of generator.

The generator is attached to the turbine. When the turbine rotates, the generator also starts rotating with it. Thanks to electromagnetic induction, the electricity is produced in the coil attached to the generator when it rotates.

Hence, from above, it is obvious that kinetic energy is converted into electric energy.

3 0
3 years ago
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What are the effects of ultraviolet sun rays????​
pychu [463]

Answer: UV rays, either from the sun or from artificial sources like tanning beds, can cause sunburn. Exposure to UV rays can cause premature aging of the skin and signs of sun damage such as wrinkles, leathery skin, liver spots, actinic keratosis, and solar elastosis. UV rays can also cause eye problems.

Explanation: Uv means ultraviolet

3 0
3 years ago
A student drops a ball from the top of a 10-meter tall building. The ball leaves the thrower's hand with a zero speed. What is t
Sergio [31]

Answer:

14 m/s

Explanation:

u = 0, h = 10 m, g = 9.8 m/s^2

Use third equation of motion

v^2 = u^2 + 2 g h

Here, v be the velocity of ball as it just strikes with the ground

v^2 = 0 + 2 x 9.8 x 10

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v = 14 m/s

7 0
3 years ago
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algol [13]
Atomic Number
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