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
Mu wildest guess is c 1500
so your saying the start is 0 N and when he/she hits the ball its inertia is 3 N. if that is so m*v=
.05*3=<u>.15</u>
Answer:
The value is 
The direction is into the surface
Explanation:
From the question we are told that
The mass density is 
The coefficient of kinetic friction is
The current the wire carries is 
Generally the magnetic force acting on the wire is mathematically represented as

Here
is the frictional force which is mathematically represented as

While
is the magnetic force which is mathematically represented as

Here
is the angle between the direction of the force and that of the current
So

So

=> ![B = \mu_k * \frac{m}{L} * [\frac{g}{I} ]](https://tex.z-dn.net/?f=B%20%20%3D%20%20%5Cmu_k%20%2A%20%20%5Cfrac%7Bm%7D%7BL%7D%20%2A%20%5B%5Cfrac%7Bg%7D%7BI%7D%20%5D)
=> ![B = 0.25 * 0.117 * [\frac{9.8}{1.24} ]](https://tex.z-dn.net/?f=B%20%20%3D%20%200.25%20%2A%20%200.117%20%20%2A%20%5B%5Cfrac%7B9.8%7D%7B1.24%7D%20%5D)
=> 
Apply the right hand curling rule , the thumb pointing towards that direction of the current we see that the direction of the magnetic field is into the surface as shown on the first uploaded image