A force F → = 2 i ^ + 3 j ^ N is applied to an object that is pivoted about a fixed axle aligned along the…

A force F → = 2 i ^ + 3 j ^  N   is applied to an object that is pivoted about a fixed axle aligned along the z-coordinate axis. If the force is applied at the point r → = 4 i ^ + 5 j ^  m,  then the magnitude of the net torque about the z-axis is
  1. 4
  2. 1
  3. 2
  4. 10

Solution

F → = 2 i ^ + 3 j ^ N

r→=4i^+5j^ m   ⇒   τ→=r→×F→

τ → = 4 i ^ + 5 j ^ × 2 i ^ + 3 j ^

τ → = 1 2 k ^ - 1 0 k ^     ⇒    τ → = 2 k ^

Asked in: JEE Mains - Rotational Motion - Test 2

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