Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main202621 January 2026Morning ShiftPhysicsLaws of MotionActual

A 4 kg mass moves under the influence of a force F = (4 t³ i -3 t j ) N where t is the time in second. If mass starts from origin at t=0 , the velocity and position after t=2 ~s will be:

Options

  1. Av =4 i - 3 2 j r = 6 5 i - j
  2. Bv =3 i + 3 2 j r = 6 5 i + j
  3. Cv =4 i - 3 2 j r = 8 5 i - j
  4. Dv =4 i + 5 2 j r = 8 5 i +2 j

Correct answer

C. v =4 i - 3 2 j r = 8 5 i - j

Step-by-step solution

Given F = (4t^3 i - 3t j ) N, m = 4 kg a = F m = t^3 i - 3t 4 j Integrating with v (0) = 0 : v = t^4 4 i - 3t^2 8 j At t = 2 : v = 16 4 i - 12 8 j = 4 i - 3 2 j Integrating with r (0) = 0 : r = t^5 20 i - t^3 8 j At t = 2 : r = 32 20 i - 8 8 j = 8 5 i - j

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 JEE Main PYQs