Answer with Explanation:
We are given that
Force acts on a pebble=
N
Position vector=
m
a.We have to find the resulting torque on the pebble about origin.
Torque=
Substitute the values then we get

Torque=
N-m
By using 
b.

Torque about point (2,0,-3)

N-m
Answer:
340.67 kgm²/s
Explanation:
R = Radius of merry-go-round = 1.9 m
I = Moment of inertia = 209 kgm²
= Initial angular velocity = 1.63 rad/s
m = Mass of person = 73 kg
v = Velocity = 4.8 m/s
Initial angular momentum is given by

The initial angular momentum of the merry-go-round is 340.67 kgm²/s
Answer: - 25.2 kgm/s
Explanation: The mass of the ball is 0.5kg, and the initial velocity = 10.6m/s.
The final velocity is in opposite direction of the initial hence final velocity (v) = - 19.9 m/s
Impulse = change in momentum = final momentum - initial momentum.
Final momentum = mass × final velocity
Final momentum = - 19.9 × 0.5
Final momentum = - 9.95 kgm/s
Initial momentum = mass × initial velocity
Initial momentum = 0.5 × 10.6 = 5.3kgm/s
Change in momentum = final momentum - initial momentum = - 19.9 - 5.3
Change in momentum = - 25.2 kgm/s
The negative sign implies that the change in momentum is the opposite direction relative to the first.
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