To solve this problem it is only necessary to apply the kinematic equations of angular motion description, for this purpose we know by definition that,
Where,
Angular Displacement
Angular Acceleration
Angular velocity
Initial angular displacement
For this case we have neither angular velocity nor initial angular displacement, then
Re-arrange for 
Replacing our values,
Therefore the ANgular acceleration of the mass is 
The correct choice is
D. 22 Hz and 42 Hz.
In fact, the beat frequency is given by the difference between the frequencies of the two waves:
In this problem, the beat frequency is 
, therefore the only pair of frequencies that gives a difference equal to 20 Hz is
D. 22 Hz and 42 Hz.
Answer:
There is absolutely No relationship between the weight of an object (which is constant) and the frictional force. If a block is sliding on a surface, that surface will be exerting a force on the block. That force can be resolved into a component parallel to the surface (which we call the frictional component), and a component perpendicular to the surface (called the normal component). For many situations, we find experimentally that the frictional component is approximately proportional to the normal component. The frictional component divided by the normal component is defined to be a quantity called the coefficient of kinetic or sliding friction. The coefficient of kinetic friction obviously depends on the nature of the surfaces involved. The normal component on an object can be decreased if you pull in the direction of the normal component (the weight does not change). However pulling this way on the object not only decreases the normal component, but it also decreases the frictional component since they are proportional. This is why it is easier to slide something if you pull up on it while you push it. If you push down, the normal and frictional components increase so it is harder to slide the object. The weight of an object is the downward force exerted by Earth’s gravity on that object, and it does not change no matter how you push or pull on the object.
Answer:
7.401 * 10^(-15) N
Explanation:
30 electrons will have a charge:
30 * -1.6022 * 10^(-19) C
= - 4.806 * 10^(-18) C
The relationship between electric field and electric force is:
E = F/q
This means that force, F, is
|F| = |E|*|q|
|F| = |1540| * |-4.806 * 10^(-18)|
|F| = |-7401.24 * 10^(-18)|
|F| = 7.401 * 10^(-15) N
All that business about the crane and the rope and the falling
is only there to confuse us.
The piano ended up 5 meters above the ground.
Potential energy = (mass) (gravity) (height)
= (200 kg) (9.81 m/s²) (5 m)
= (200 · 9.81 · 5) (kg-m²/s²)
= 9,810 joules .
