Answer: MR²
is the the moment of inertia of a hoop of radius R and mass M with respect to an axis perpendicular to the hoop and passing through its center
Explanation:
Since in the hoop , all mass elements are situated at the same distance from the centre , the following expression for the moment of inertia can be written as follows.
I = ∫ r² dm
= R²∫ dm
MR²
where M is total mass and R is radius of the hoop .
Answer:
The input force (effort) is the amount of effort used to push down on a rod, or pull on a rope in order to move the weight. In this example, the force the little guy is using to pull the elephant is the input force.
Explanation:
Answer:
Angular acceleration, is 
Explanation:
Given that,
Initial speed of the drill, 
After 4.28 s of constant angular acceleration it turns at a rate of 28940 rev/min, final angular speed, 
We need to find the drill’s angular acceleration. It is given by the rate of change of angular velocity.

So, the drill's angular acceleration is
.
Answer:
3.63 s
Explanation:
We can solve the problem by using the equivalent SUVAT equations for the angular motion.
To find the angular acceleration, we can use the following equation:

where
is the final angular speed
is the initial angular speed
is the angular distance covered
is the angular acceleration
Re-arranging the formula, we can find
:

Now we want to know the time the bit takes starting from rest to reach a speed of
. So, we can use the following equation:

where:
is the angular acceleration
is the final speed
is the initial speed
t is the time
Re-arranging the equation, we can find the time:

Answer:
1/2
Explanation:
The energy stored in a capacitor is given by

where
C is the capacitance
V is the potential difference
Calling
the capacitance of capacitor 1 and
its potential difference, the energy stored in capacitor 1 is

For capacitor 2, we have:
- The capacitance is half that of capacitor 1: 
- The voltage is twice the voltage of capacitor 1: 
so the energy stored in capacitor 2 is

So the ratio between the two energies is
