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Questions in physics

📝 Answered - 64. An atom has 11 protons and 12 neutrons. Then the number of electrons in this atom is A. 12 B. 11 C. 23 D. 1 65. 100 J of mechanical energy is supplied to 1 kg water which raises its temperature through A. 100 K B. 4200 K C. [tex]$\left(\frac{1}{4200}\right)^{ K }$[/tex] D. [tex]$\left(\frac{1}{42}\right)^{ K }$[/tex] 66. A person suffering from myopia has to use A. biconvex lens B. planoconvex lens C. biconcave lens D. concavoconvex lens 67. An object is placed at a distance of 20 cm from a convex lens of focal length 10 cm. The image formed by the lens will be A. at 20 cm from the lens, inverted and real B. at 20 cm from the lens, inverted and virtual C. at 20 cm from the lens, erect and real D. at 20 cm from the lens, erect and virtual 68. To find the direction of induced current in an electromagnetic induction, A. Maxwell's cork screw rule is used B. Right hand thumb rule is used C. Fleming's right hand rule is used D. Fleming's left hand rule is used

📝 Answered - Find the uncertainty in velocity, if the uncertainty in position is equal to the uncertainty in momentum. a) [tex]$\frac{h}{\sqrt[2]{\pi m}}$[/tex] b) [tex]$\frac{1}{2 m} \sqrt{\frac{h}{\pi}}$[/tex] c) [tex]$\frac{1}{m} \sqrt{\frac{h}{\pi}}$[/tex] d) [tex]$\frac{1}{2} \sqrt{\frac{h}{m \pi}}$[/tex]

📝 Answered - The uncertainty involved in the measurement of velocity within a distance of [tex]$0.1 A^0$[/tex] is: a) [tex]$5.79 \times 10^6 m / s$[/tex] b) [tex]$5.79 \times 10^7 m / s$[/tex] c) [tex]$5.79 \times 10^8 m / s$[/tex] d) [tex]$5.79 \times 10^5 m / s$[/tex]

📝 Answered - Find the magnitude and direction of the net electric field at point A. The two particles in the diagram each have a charge of +3.1 µC. The distance separating the charges is 9.0 cm. The distance between point A and B is 6.0 cm.

📝 Answered - A ball bearing is placed on an inclined plane and begins to roll. The angle of elevation of the plane is [tex]$\theta$[/tex]. The distance (in meters) the ball bearing rolls in [tex]$t$[/tex] seconds is [tex]$s(t)=4.9(\sin (\theta)) t^2$[/tex]. (a) Determine the speed (in meters per second) of the ball bearing after [tex]$t$[/tex] seconds. (b) Complete the table. | | | [tex]$\frac{\pi}{4}$[/tex] | [tex]$\frac{\pi}{3}$[/tex] | [tex]$\frac{\pi}{2}$[/tex] | | :-----------------: | :-: | :-----------------: | :-----------------: | :-----------------: | | [tex]$s^{\prime}(t)$[/tex] | | | | | | [tex]$\theta$[/tex] | [tex]$\frac{2 \pi}{3}$[/tex] | [tex]$\frac{3 \pi}{4}$[/tex] | [tex]$\pi$[/tex] | | :-----------------: | :-----------------: | :-----------------: | :-----------------: | | [tex]$s^{\prime}(t)$[/tex] | | | | Use the table to determine the value of [tex]$\theta$[/tex] that produces the maximum speed at a particular time.

📝 Answered - Who is quoted as saying "The eternal mystery of the world is its comprehensibility... the fact that it is comprehensible is a miracle"? A. Albert Einstein B. Stephen Hawking C. John Polkinghorne D. John Lennox

📝 Answered - An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?

📝 Answered - What is the term for producing a current by moving a wire through a magnetic field? solenoid induction flowing induction electromagnetic induction coiled induction

📝 Answered - An electric device delivers a current of [tex]$15.0 A$[/tex] for 30 seconds. How many electrons flow through it?

📝 Answered - Two particles have position vectors given by: [tex]\begin{array}{l} \overrightarrow{r_1}=2 t i-t^2 j+\left(3 t^2-4 t\right) k \\ \overrightarrow{r_2}=(5 t-12 t+4) i+t^3 j-3 t k \end{array}[/tex] Express in vector form, the relative velocity of the 2nd particle with respect to the 1st particle.