Doubtly
@Doubtly · Joined Feb 2021
- Answers
- 3,792
- Questions
- 4,033
- Upvotes received
- 424
- If the current flowing in a coil is reduced to half of its original value, The Correct option is D) E₂ = 1over4 E_(1 ) Explaination Current is become half of the given value. E=1over2Li² i.e. E₂over E₁=(i₂over i₁)²=... 1
- evaluate int x-1/(x+1)^3 e^x dx {integration question } The correct answer is e^xover (x+1)²+c Explaination: 1
- l,m,n are the pth and rth term of G.P all positive then Correct option is 4) 0 Let x and y are first term and common ratio of GP respectively. first and second row are identical =0 1
- A time-dependent force F = 6t acts on a particle of mass 1 kg. If the particle starts from rest, the work done by the force during the first 1 sec. will be : The correct option is c) 4.5 J F= 6t, m = 1Kg, u =0 Now, F=ma =m(dv/dt)=1x(dv/dt) dv/dt = 6t ∫ ^v₀dv =∫¹₀6tdt v= 3(1²– 0) = 3m/s From work-e... 1
- At time t = 0s particle starts moving along the x-axis. If its kinetic energy increases uniformly with time ‘t’, The correct option is d) 1/√(t) Linear dependency with initial Kinetic Energy as zero is given as KE = kt, where k is the proportionality co... 1
- Two masses of 1 g and 4g are moving with equal kinetic energy. The ratio of the magnitudes of their momenta is The correct option is c)1:2 p=√(2Em) Where p denotes momentum, E denotes kinetic energy and mdenotes mass. p₁over p₂=√(m₁over m₂) p₁over p₂... 1
- A body of mass m=10−2 kg is moving in a medium and experiences a frictional force F=−kv2. Its initial speed is v0= 10 ms−1. (c) 10⁻⁴ kg m−1 is the correct answer Mass m = 10² Kg Initial velocity v₀= 10 ms⁻¹ Time t = 10 s Frictional Force F=− kv² 1/2 mv_f^(2 )= ⅛ m... 1
- Consider a car moving on a straight road with a speed of 100 m/s. The distance at which a car can be stopped is : (μk = 0.5) b) is the correct option i.e. 1000 When the car is stopped by friction then its retarding force is ma = μR ma = μmg a= μg Consider the equat... 1
- 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 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