A) 
The total energy of the system is equal to the maximum elastic potential energy, that is achieved when the displacement is equal to the amplitude (x=A):
(1)
where k is the spring constant.
The total energy, which is conserved, at any other point of the motion is the sum of elastic potential energy and kinetic energy:
(2)
where x is the displacement, m the mass, and v the speed.
We want to know the displacement x at which the elastic potential energy is 1/3 of the kinetic energy:

Using (2) we can rewrite this as

And using (1), we find

Substituting
into the last equation, we find the value of x:

B) 
In this case, the kinetic energy is 1/10 of the total energy:

Since we have

we can write

And so we find:

If the gymnast mass were doubled, her height (h) from the top of the board would be as follows,
с Stay the same
Explanation:
- The Mass of an object or body does not affect the acceleration due to gravity in any kind of way.
- Light weight objects accelerate more slowly than the heavy objects because when the forces other than the gravity also plays a major role.
- Mass increases of a body when an object has higher velocity or the speed.
- The greater the force of gravity, it would give a direct impact on the object's acceleration; thus considering only a force, the heavier the object is, it would accelerate faster. But an acceleration depends upon the two factors which are force and mass.
- Newton's second law of motion states that the acceleration of an object is dependent upon the two factors which are, the net force of an object and the mass of the object.
To solve this problem it is necessary to apply the concepts related to the conservation of the Momentum describing the inelastic collision of two bodies. By definition the collision between the two bodies is given as:

Where,
= Mass of each object
= Initial Velocity of Each object
= Final Velocity
Our values are given as




Replacing we have that



Therefore the the velocity of the 3220 kg car before the collision was 0.8224m/s
In order to create a charged object you need to transfer electrons either away or to the object by induction, conduction, or friction
Induction is without contact(like bringing a charged object to a electroscope charges the leaves at the bottom)
Conduction is with contact(like the previous answer, wore touching transfers the charge from a source to the object)
Friction(rubbing a balloon on wool)