Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
99 Percentile Qs Bank for JEE MainPhysicsLaws of Motion

A small coin of mass 40   g is placed on the horizontal surface of a rotating disc. The disc starts from rest and is given a constant angular acceleration α = 2   rad   s - 2 . The coefficient of static friction between the coin and the disc is μ s = 3 / 4 and the coefficient of kinetic friction is μ k = 0.5 . The coin is placed at a distance r = 1   m from the centre of the disc. T

Options

  1. A0 . 2 N
  2. B0 . 3   N
  3. C0 . 4   N
  4. D0 . 5 N

Correct answer

D. 0 . 5 N

Step-by-step solution

The friction force on coin just before coin is to slip will be : f = μ s mg Normal reaction on the coin ; N = mg The resultant reaction by disk to the coin is = N 2 + f 2 = mg 2 + μ s mg 2 = mg 1 + μ s 2 = 4 0 × 1 0 - 3 × 1 0 × 1 + 9 1 6 = 0.5 N

Practice Laws of Motion on Quantrex Academy →

More from Laws of Motion

A block takes t time to slide down a plane inclined at 45° to the horizontal. If the surface is made smooth (frictionless), the block takes time t 2 to slide down the plane. The co 2026Two blocks ( P and Q ) with respectively masses 2 kg and 1.5 kg are joined by a massless thread. These blocks are mounted on a frictionless pulley which is fixed on the edge of a c 2026A mass of 1 kg is kept on an inclined plane with 30° inclination with respect to horizontal plane and it is at rest initially. Then the whole assembly is moved up with constant vel 2026Three masses m₁ = 4 kg, m₂ = 4 kg and m₃ = 6 kg are suspended from a fixed smooth frictionless pulley as shown in the figure below. The value of T₁/T₂ is _____. (take g = 10 m/s ^2 2026A wedge Y with mass of 10 kg and all frictionless surfaces and the inclined surface making 37° with horizontal. A block X with mass 2 kg is placed at the highest point of the wedge 2026At t=0 , a body of mass 100 g starts moving under the influence of a force (5 i +10 j ) N. After 2 s its position is (2x i +5y j ) m. The ratio x:y is ______. 2026The time taken by a block of mass m to slide down from the highest point to the lowest point on a rough inclined plane is 50 % more compared to the time taken by the same block on 2026A 0.5 kg mass is in contact against the inner wall of a cylindrical drum of radius 4 m rotating about its vertical axis. The minimum rotational speed of the drum to enable the mass 2026 Full Laws of Motion list All 99 Percentile Qs Bank for JEE Main PYQs