Physics, Chemistry, Mathematics Forums

What causes radioactivity? What is the atomic structure of atoms of radioactive elements?

Two friends decide to meet between 10am to 11am in a cafe. The first one arrived and waited for 20 minutes and left . What is the probability that they both meet?

The answer is 5/9 but I can't get the process.

Q#1: A pair of positive integers x0 and y0 are selected and further pairs are generated according to the following rule: After the values of xn and yn have been found, a coin is tossed. If it lands heads, then xn+1 = xn −1 and yn+1 = xn. Otherwise, if it lands tails, then xn+1 = yn − 2 and yn+1 = xn + 1. The process ends when a non-positive value of x or y is generated. Is there a choice of initial values for x0 and y0 and sequence of coin toss outcomes for which the sequence of x’s and y’s does not terminate? 

What is potential drop? how it is calculated? piease explain with example........

Let an infinite grid of resistors (figure), but in 3 dimensions. Calculate the equivalent resistence between two consecutive nodes.

R = 1 ohm

abhishek wrote 6 letters to 6 friends. He wants to post these in addressed envelops. By how many ways 4 letters have gone into wrong envelops?

Find the number of permutations of n different things taken r at a time such that the two specified things occur together?

Hello Friends,

Please solve these questions.

Q(1):- The n-factor of CuCN in the given reaction is:-

          CuCN -----------> Cu⁺²  +  CO₂  +  HNO₃

          (A) 11

          (B) 7

          (C) 9

          (D) 3

Ans(1):- The answer is (A). But kindly explain me the reason.

Q(2):- The Oxidation Number of Cr in CrO₅ is

          (A) +10

          (B) +7

          (C) +6

          (D) +4

Ans(2):- The answer appears to be (A) i.e. +10 but this is not so. The anwer is (C) i.e. +6. Why is it so?

A block of weight 100 N is slowly slid up on a smooth incline of inclination 37⁰ by a person. Calculate the work done by the person in moving the block through a distance of 2 m, if the driving force is a) parallel to the incline and b) in the horizontal direction.

Ans : a) 120J   b)120J. Please explain how to solve this question.

The product of the slope of two perpendicular lines is -1 i.e. m1.m2=-1.

They why does not the product of the x-axis and y-axis be -1 though they are perpendicular to one another?