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son4ous [18]
4 years ago
15

Define work done against friction(helpp)​

Physics
1 answer:
77julia77 [94]4 years ago
7 0

Answer:

The work done against friction is the work done on an object that overcomes this frictional force allowing the object to move - it doesn't include any extra work used to accelerate an object for example - only the work used to beat the frictional force.

Explanation:

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A military helicopter on a training mission is flying horizontally at a speed of 90.0 m/s when it accidentally drops a bomb (for
Elena-2011 [213]

Answer:

1) 10.1 s  2) 909 m 3) 90.0 m/s 4) -99m/s 5) just over the bomb.

Explanation:

1)

  • In the vertical direction, as the bomb is dropped, its initial velocity is 0.
  • So, we can find the time required for the bomb to reach the earth, applying the following kinematic equation for displacement:

       \Delta y = \frac{1}{2}*a*t^{2} (1)

  • where Δy = -500 m (taking the upward direction as positive).
  • a=-g=-9.8 m/s²
  • Replacing these values in (1), and solving for t, we have:

       t =\sqrt{\frac{2*\Delta y}{-g}} = \sqrt{\frac{2*(-500m)}{-9.8m/s2}} = 10.1 s

  • The time required for the bomb to reach the earth is 10.1 s.

2)

  • In the horizontal direction, once released from the helicopter, no external influence acts on the bomb, so it will continue moving forward at the same speed. that it had, equal to the helicopter.
  • As the time must be the same for both movements, we can find the horizontal displacement just as the product of this speed times the time, as follows:

       x = v_{0x} * t = 90.0 m/s * 10.1 s = 909 m.

3)

  • The horizontal component of the bomb's velocity is the same that it had when left the helicopter. i.e. 90 m/s.

4)

  • In order to find the vertical component of the bomb's velocity just before it strikes the earth, we can apply the definition of acceleration, remembering that v₀ = 0, as follows:

        v_{f} = -g*t = -9.8 m/s2*10.1 s = -99 m/s

5)

  • If the helicopter keeps flying horizontally at the same speed, it will be always over the bomb, as both travel horizontally at the same speed.
  • So, when the bomb hits the ground, the helicopter will be exactly over it.

8 0
4 years ago
A runner starts from rest, runs for 30
aleksklad [387]

Answer:

u=0

t=30s

a=2m/s²

v=?

v= u+at

= 0+(30)(2)

= 60m/s

6 0
3 years ago
A pulley in the shape of a solid cylinder of mass 1.50 kg and radius 0.240 m is free to rotate around a horizontal shaft along t
liq [111]

Answer:

the speed of the textbook just before it hits the floor is 2.4 m/s

Explanation:

  Given the data in the question;

mass of pulley = 1.50 kg

radius of pulley = 0.240 m

mass of text book = 2.0 kg

height from which text book was released = 0.9 m

angular speed of the pulley = 10.0 rad/s

the speed of the textbook just before it hits the floor = ?

the speed of the textbook v = angular speed of the pulley × radius of pulley

we substitute

v = 10.0 rad/s × 0.240 m

v = 2.4 m/s

Therefore, the speed of the textbook just before it hits the floor is 2.4 m/s

6 0
3 years ago
A physics student mounts two thin lenses along a single optical axis (the lenses are at right angles to the line connecting them
Tatiana [17]

Answer:

A)    q₂ = 75.98 cm, B)     q₂' = 115.38 cm, C)

Explanation:

A) This is an exercise in geometric optics, as the two lenses are separated by a greater distance than their focal lengths from each lens, they must be worked as independent lenses.

Lens 1. More to the left

let's use the constructor equation

         \frac{1}{f} = \frac{1}{p} + \frac{1}{q}

where f is the focal length, p and q are the distance to the object and the image, respectively,

We must assume a distance to the object to perform the calculation, suppose that the object is 50 cm from lens 1 that is further to the left of the system.

          \frac{1}{q_1} = \frac{1}{f} - \frac{1}{p}

         \frac{1}{q_1} = \frac{1}{14.8} - \frac{1}{50}  

          1 / q₁ = 0.04756

           q₁ = 21.0227 cm

this image is the object for the second lens that has f₂ = 14.8 cm

the distance must be measured from the second lens

          p₂ = 39.4 -q₁

          p₂ = 39.4 -21.0227

          p₂ = 18.38 cm

let's use the constructor equation

            1 / q₂ = 1 / f - 1 / p2

             

             \frac{1}{q_2} = \frac{1}{14.8} - \frac{1}{18.38}

            \frac{1}{q_2} = 0.01316

            q₂ = 75.98 cm

measured from the second lens

B) the position of the final image with respect to the first lens is

            q₂’= q₂ + 39.4

             q₂'= 75.98 +39.4

              q₂' = 115.38 cm

C) the magnification of a lens is

              m = - q / p

in this case the image measured from lens 2 is q2 = 75.98 cm

the distance to the object from the first lens is p1 = 50cm

          m = - 75.98 / 50

          m = -1.5 X

the negative sign indicates that the image is inverted

4 0
3 years ago
Protons and neutrons in an atom are held together by _____.
marysya [2.9K]
Protons and neutrons in an atom are held together by a nuclear energy also called the strong force.
7 0
4 years ago
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