Answer: A) 
Explanation:
The equation for the moment of inertia
of a sphere is:
(1)
Where:
is the moment of inertia of the planet (assumed with the shape of a sphere)
is the mass of the planet
is the radius of the planet
Isolating
from (1):
(2)
Solving:
(3)
Finally:
Therefore, the correct option is A.
Answer:
The distance travel by block before coming to rest is 0.122 m
Explanation:
Given:
Mass of block
kg
Initial speed of block

Final speed of block

Coefficient of kinetic friction 
Ramp inclined at angle
28.4°
Using conservation of energy,
Work done by frictional force is equal to change in energy,

Where 



m
Therefore, the distance travel by block before coming to rest is 0.122 m
Answer:34 cm
Explanation:
Given
mass of meter stick m=80 gm
stick is balanced when support is placed at 51 cm mark
Let us take 5 gm tack is placed at x cm on meter stick so that balancing occurs at x=50 cm mark
balancing torque






To solve this problem, we must imagine that Jim’s initial
position, the position of the rock, and Jim’s final position all connects to
form a triangle. Now we can imagine that the triangle is a right triangle with
the 90° angle on the initial position.
The angle of 30° is directly opposite to the length of his
total stride while the width of the river is the side adjacent to the angle.
Therefore can use the tan function to solve for the width of the river:
tan θ = opposite side / adjacent side
tan 30 = total stride distance / width of river
where total stride distance = 65 * 0.8 = 52 m
width of river = 52 m / tan 30
<span>width of river = 90.07 m</span>