Doubtly
@Doubtly · Joined Feb 2021
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- A smooth block is released at rest on a 45∘ incline and then slides a distance The correct answer is a) µk = 1 - 1/n^(2 ) ^(Solution::) On a smooth plane d = ½ (g sinθ) t₁ _( t₁=√( 2dover gsinθ) ) On a rough surface d =... 2
- A marble block of mass 2 kg lying on ice when given a velocity of 6 m/s is stopped by friction in 10s. Then the coefficient of friction is (consider g =10m/s) The correct option is c) 0.06 Explaination: u = 6 m/s v = 0 t =10s a = -f/m = – μmg/m = – μg = -10μ Substituting values in v = u+at 0 = 6 –... 1
- A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is 0.2. The correct option is d) 2N Frictional force balances the weight of the body Frictional force f = μN = mg f= 0.2 X 10 = 2N Therefore, weight... 1
- During the padding of a bicycle, the force of friction exerted by the ground on the two wheels is such that it acts The correct option is a) in the backward direction on the front wheel and in the forward direction on the rear wheel Explaination:: In the b... 1
- The number of seven digit integers, with sum of the digits equal to 10 and formed by using the digits 1, 2 and 3 only, is The correct answer is option C) 77 solution:: there can be two cases numbers can be case 1 :: 1, 1, 1, 1, 2, 2, 2 possible 7 digits number b... 1
- If a, b, c are odd positive integers, then number of integral solutions of a + b + c = 13, is The correct answer is option b) 21 explaination :: Let a = 2k + 1, b = 2l + 1, c = 2m + 1 where k, l, m are whole number a + b + c = 13 2k +... 1
- The total number of positive integral solution for x, y, z such that xyz = 24, is The correct answer is option a)30 solution::: xyz = 24 xyz = 2³ × 3¹ The number of ways of distributing 'n' identical balls into 'r' differe... 1
- Two numbers are chosen from 1, 3, 5, 7,… 147, 149 and 151 and multiplied together in all possible ways. The correct answer is d) 1020 In the given numbers 1, 3,5,7,…, 147, 148, 151the numbers which are multiple of 5 are 5, 15, 25, 35,…, 145 whi... 1
- Ammonolysis of alkyl halide to prepare primary, secondary and tertiary amines followed by NaOH is The correct answer is option 1 to remove acidic impurities 2
- A planet is revolving around sun in elliptical orbit. Maximum & minimum distance of planet from sun are respectively 1.6 × 1012 m and 6 × 1010 m. Answer: (2) 3 × 10³ m/s Gravity on the planet acts along the line to the Sun, so the planet's angular momentum about the Sun is conserved. A... 1
- A particle of mass m1 = m moving with velocity 10root3 m/s ˆ i collides with a particle of mass m2 = 2m at rest. Correct answer is 30 vec p_f=vec p_i M × 10 hat j + m vec v = m × 10 sqrt 3hat i vec v=10sqrt3 hat i+10hat j 2
- A particle of mass rotates in a circle which has a vertical boundary of radius 0.2 meter, rotating in horizontal plane. The correct option is option 1) 9.8 × 10^(–4) N N=mω²R =(0.2)[ 4π²over T²](R) =0.24(9.8)over 1600(0.2) =9.8×10⁻⁴ N 1
- A bar magnet of length 14 cm is placed along N-S direction with north of magnetic along north direction. If horizontal component The correct option is 1) 2.88 Am^(2 ) 1
- An antenna of length 25 m is mounted on top of a building of height 75 m. The correct option is 1)100 m Length of antenna ≥ λover 4 λ ≤ 4×25 λ ≤100m 1
- Three gases O2, N2 and Co2 having masses 16g, 28g and 44g respectively are filled in a container of volume V The correct option is 4) 5over 2 RTover V PV=(16over32+ 28over28+ 44over44)RT p=5over 2 RTover V 1
- Four small balls are placed at the corner of a square of length l. Evaluate MOI of system about a line passing through A and parallel to BD. The correct option is 2) 3 ml² I=2m(loversqrt2)² +m(sqrt2l)² =2ml²over 2+2ml²=3ml² 1
- In photoelectric effect stopping potential for electromagnetic radiations depends on Correct option is 4)frequency In photoelectric effect stopping potential for electromagnetic radiations depends on frequency 1
- A simple pendulum attached to ceiling of lift has time period T when lift is at rest. The correct option is 1) √(2over 3)T T=2π lover g T'=2π lover g+gover2 therefore T'over T= sqrt gover 3g over2 T'=Tsqrt 2over3 1