A particle, mass 0.25 kg is at a position () m, has a velocity () m/s, and is subject to a force () N. What is the magnitude of the torque on the particle about the origin

Question

A particle, mass 0.25 kg is at a position (-7i + 7j + 5k) m, has a velocity (6i - j + 4k) m/s, and is subject to a force (-5i + 0j - k) N. What is the magnitude of the torque on the particle about the origin?

47.94Nm

Explanation:

The torque (τ) on a particle subject to a force (represented as force vector F) at a position (represented as position vector r) about the origin is given by the cross product of the position vector r for the point of application of a force and the force F. i.e

τ = r x F

Given:

r = (-7i + 7j + 5k) m

F = (-5i + 0j - k) N

                    |   i             j              k    |

r x F  =         |   -7            7              5  |

                    |  -5           0              -1   |

r x F  =       i(-7 - 0) - j(7+25) + k(0+35)

r x F  =       i(-7) - j(32) + k(35)

r x F  =       -7i - 32j + 35k

Therefore the torque τ = -7i - 32j + 35k

The magnitude of the torque is therefore;

|τ| =

|τ| =

|τ| =

|τ| = 47.94Nm

The magnitude of the torque on the particle about the origin is 47.94Nm

2.77 x 10^-3 its for plato user 

At maximum height, kinetic energy is converted in potential energy  formula: at max height, ke = ½ * 0.27kg * (16m/s) ² = 34.56 j  so the remaining pe = (41.70 – 34.56)= 7.14 j = 0.27 kg * 9.8m/s² * h  = (9.8/7.14 * 0.27)so max height h = 5.08 or 5 m