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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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During a cold winter night a car unfortunately skids to a stop shortly before crashing into a donut shop. The skid marks are 34.
horsena [70]

Answer: The car was moving with the speed of 14.13 m/s.

Explanation:

Length of the skid marks,d = 34 m

Mass of the car = 825 kg

Coefficient of friction = \mu =0.300

Velocity of the car after applying the brakes =v

Acceleration due gravity = 9.8 m/s^2

d=\frac{v^2}{2\mu g}

34 m=\frac{v^2}{2\times 0.300\times 9.8 m/s^2}

v^2=34 m\times 2\times 0.300\times 9.8 m/s^2=199.92 m^2/s^2

v = 14.13 m/s

The car was moving with the speed of 14.13 m/s.

7 0
4 years ago
What are the distinguishing properties of objects in our solar system?
Ostrovityanka [42]

Answer:uranus

Explanation:it sounds weird

3 0
3 years ago
A ledge on a building is 20 m above the ground. A taut rope attached to a 4.0 kg can of paint sitting on the ledge passes up ove
Andrews [41]

Answer:

 t = 5.4 s

Explanation:

from the question we are given :

height (s) = 20 m

mass of paint (Mp) = 4 kg

mass of nails (Mn) = 3 kg

acceleration due to gravity (g) = 9.8 m/s^{2}

  • The net force accelerating the can of paint should be equal to the difference in weight of the can of paint and the can of nails.

            weight of nails = mass of nails x g = 3 x 9.8 = 29.4 N

            weight of paint = mass nails x g = 4 x 9.8 = 39.2 N

             net force = 39.2 - 29.4 = 9.8 N

  • net force = total mass x acceleration

             9.8 = (3 +4) x a

              a = 1.4 m/s^{2}

  • from S = Ut + 0.5at^{2}  we can get  the time the carpenter has to catch the nails

          where U is the initial velocity and is 0 since the can was initially at            

            rest

           20 = (0 x t) + (0.5 x 1.4 x t^{2})

            20 = 0.7 x t^{2}

             t^{2} = 28.6

             t = 5.4 s

                   

         

8 0
3 years ago
What does it mean when the
vfiekz [6]

Answer:

it will option B,hope it helps

7 0
3 years ago
Disabling asthma attacks can lead to restrictive school activity of approximately
mamaluj [8]

Answer:

<h2>Yes.</h2>

Explanation:

If we want to "disable" astham attacks, that would imply too many restictions for those people who can suffer from these attacks. For example, in order to avoid these attacks, they couldn't do sport activities, because that would alter their respiratory system, which occasionate astham attacks.

Therefore, this statement is true.

7 0
3 years ago
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