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vesna_86 [32]
3 years ago
15

The focal length for a spherical convex mirror is –20 cm. What is its radius of curvature?

Physics
1 answer:
Svetradugi [14.3K]3 years ago
4 0

Answer:

40 cm

Explanation:

The focus of a spherical convex mirror is the point at which the rays of an object converge in the infinite, it is also the point at which an object must be placed so that its image is formed in the infinite. The distance from the focus to the origin is called the focal length and is called f. It is related to the radius of the mirror, R, according to:

f=-\frac{R}{2}

rewriting for R:

R=-2f=-2*-20cm=40 cm.

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Block B is attached to a massless string of length L = 1 m and is free to rotate as a pendulum. The speed of block A after the c
Amanda [17]

Complete Question

The diagram for this question is shown on the first uploaded image

Answer:

The minimum velocity of A is  v_A= 4m/s

Explanation:

From the question we are told that

    The length of the string is  L = 1m

     The initial speed of block A is u_A

     The final speed of block A is  v_A = \frac{1}{2}u_A

      The initial speed of block B is u_B = 0

      The mass of block A  is  m_A = 7kg  gh

      The mass of block B is  m_B  = 2 kg

According to the principle of conservation of momentum

       m_A u_A + m_B u_B = m_Bv_B + m_A \frac{u_A}{2}

Since block B at initial is at rest

       m_A u_A  = m_Bv_B + m_A \frac{u_A}{2}

      m_A u_A  - m_A \frac{u_A}{2} = m_Bv_B

          m_A \frac{u_A}{2} = m_Bv_B

  making v_B the subject of the formula

             v_B =m_A \frac{u_A}{2 m_B}

Substituting values

               v_B =\frac{7 u_A}{4}  

This v__B is the velocity at bottom of the vertical circle just at the collision with mass A

Assuming that block B is swing through the vertical circle(shown on the second uploaded image ) with an angular velocity  of v__B' at  the top of the vertical circle  

 The angular centripetal acceleration  would be mathematically represented

                   a= \frac{v^2_{B}'}{L}

Note that  this acceleration would be toward the center of the circle

      Now the forces acting at the top of the circle can be represented mathematically as

         T + mg = m \frac{v^2_{B}'}{L}

    Where T is the tension on the string

  According to the law of energy conservation

The energy at  bottom of the vertical circle   =  The energy at the top of

                                                                                the vertical circle

   This can be mathematically represented as

                 \frac{1}{2} m(v_B)^2 = \frac{1}{2} mv^2_B' + mg 2L

From above  

                (T + mg) L = m v^2_{B}'

Substitute this into above equation

             \frac{1}{2} m(\frac{7 v_A}{4} )^2 = \frac{1}{2} (T + mg) L  + mg 2L  

             \frac{49 mv_A^2}{16}  = \frac{1}{2} (T + mg) L + mg 2L

          \frac{49 mv_A^2}{16}  = T + 5mgL

The  value of velocity of block A needed to cause B be to swing through a complete vertical circle is would be minimum when tension on the string due to the weight of B is  zero

        This is mathematically represented as

                      \frac{49 mv_A^2}{16}  = 5mgL

making  v_A the subject

            v_A = \sqrt{\frac{80mgL}{49m} }

substituting values

          v_A = \sqrt{\frac{80* 9.8 *1}{49} }

              v_A= 4m/s

     

6 0
2 years ago
One watt is equal to which of these values?
dusya [7]
1 W = 1 J/s 
Watt<span> is the unit of measure for power .
</span><span>
</span>Joule is the unit of measure for the energy and the second is the unit of measure for time.


3 0
3 years ago
Read 2 more answers
What is the force on a 1025 kg elevator that is falling freely at 9.8 m/sec 2?
kicyunya [14]

Answer:

<h2><u>Given </u><u>:</u><u>-</u></h2>
  • Mass = 1025 kg
  • Acceleration = 9.8 m/s²
<h2><u>To </u><u>Find</u><u> </u><u>:</u><u>-</u></h2>

Force

<h2><u>Solution</u><u> </u><u>:</u><u>-</u></h2>

We know that

F = mg

F = 1025 × 9.8

F = 10,045 N

Or,

10045/1000 = 10.045 Kilo Newton

\\

6 0
2 years ago
An organism’s scientific name consists of a. its class name and its family name. b. its kingdom name and its phylum name. c. its
mr Goodwill [35]
An organism scientific name consist of : C. its genus name and its species name
The first part of the name is taken from the Genus and the second part of the name is taken from the species
hope this helps

7 0
3 years ago
Your low-flow showerhead is delivering water at 1.2×10−4m3/s, about 2.0 gallons per minute.
Oksanka [162]

To solve this problem it is necessary to apply the fluid mechanics equations related to continuity, for which the proportion of the input flow is equal to the output flow, in other words:

Q_1 = Q_2

We know that the flow rate is equivalent to the velocity of the fluid in its area, that is,

Q = VA

Where

V = Velocity

A = Cross-sectional Area

Our values are given as

Q_2 = 1.2*10^{-4}m^3/s

d = 0.021m

r = \frac{0.021}{2} = 0.0105m

Since there is continuity we have now that,

V_1A_1 = Q_2

V_1A_1 = 1.2*10^{-4}

V_1 = \frac{1.2*10^{-4}}{A_2}

V_1 = \frac{1.2*10^{-4}}{\pi r^2}

V_1 = \frac{1.2*10^{-4}}{\pi (0.0105)^2}

V_1 =0.347m/s

Therefore the speed of the water's house supply line is 0.347m/s

7 0
3 years ago
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