A particle of mass M = 0.2 kg is initially at rest in the xy-plane at a point (x = -l, y = -h), where l = 10 m and h = 1m. The particle is accelerated at time t = 0 with a constant acceleration a = 10 m/s² along the positive x-direction. Its angular momentum and torque with respect to the origin, in SI units, are represented by $\vec{L}$ and τ, respectively. î, ĵ and k̂ are unit vectors along the positive x, y and z-directions, respectively. If k̂ = î × ĵ then which of the following statement(s) is(are) correct ?
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Question

A particle of mass M = 0.2 kg is initially at rest in the xy-plane at a point (x = -l, y = -h), where l = 10 m and h = 1m. The particle is accelerated at time t = 0 with a constant acceleration a = 10 m/s² along the positive x-direction. Its angular momentum and torque with respect to the origin, in SI units, are represented by $\vec{L}$ and τ, respectively. î, ĵ and k̂ are unit vectors along the positive x, y and z-directions, respectively. If k̂ = î × ĵ then which of the following statement(s) is(are) correct ?

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G1 Physics · Accepted Answer

Use angular momentum L⃗=r⃗×p⃗ (or L=Iω for a rigid body). During a short impact, angular momentum about a point with zero impulsive torque is conserved; use linear momentum/energy additionally where applicable. This gives A: The particle arrives at the point (x = l, y = -h) at time t = 2s; B: τ = 2k̂ when the particle passes through the point (x = l, y = -h); C: L⃗ = 4k̂ when the particle passes through the point (x = l, y = -h).