Answer:
The ratio (U₁/U₂) = 6
Explanation:
U, the potential energy is given as
U = kqQ/r
k = Coulomb's constant
q = charge we're concerned about
Q = charge of the negative plate of the capacitor
r = distance of q from the negative plate of the capacitor.
For charge q₁
U₁ = kq₁Q/s
U₂ = kq₂Q/2s
But q₂ = q₁/3
U₂ becomes U₂ = kq₁Q/6s
U₁ = kq₁Q/s
U₂ = kq₁Q/6s
(U₁/U₂) = 6
Factors affecting friction
The intensity of friction depends on following factors: i) The area involved in friction. ii) The pressure applied on the surfaces. Force = Pressure ´ Area Frictional force will increase, if the area of contact will increase or if pressure applied on the surface increased.
Methods to reduce friction
i) Polish the contact surface. ii) Put oil or grease so that it fills in the small gaps of the flat parts. iii) Use ball bearings to reduce area of contact between rotating parts.
Lubrication
Following methods can be used to reduce friction: Oil is either thin or viscous. It depends upon SAE No. of oil. (SAE means Society of Automotive Engineers). If we use very viscous oil, it does not reach all the parts. Very thin oil will flows away easily and gets wasted. Grease is used in such cases. It is generally used around ball-bearing. Normal grease or oil is never used where there is high pressure, high temperature and high speed. Special lubricants are used in such cases. In cold season the oil becomes thick and in hot season it becomes thin. Therefore selection of lubrication also depends on the season. It is always advisable to refer operating manual of the equipment before selecting the lubricant.
<u>Answer:</u>
Option: D. Gravity is pulling the crash test dummy in the direction the car is moving.
<u>Explanation:
</u>
When a car accelerates from a standing start, the crash test dummy appears to be pressed backward into the seat cushion because the gravity is pulling the crash test dummy in the direction the car is moving.
Basically when the car is starting, the person inside is in static position and the car is going to move. So it is putting a force on the person to move on the same speed. But as the person is sitting static hence gravity is pulling him behind from moving. Hence, The dummy appears to be pressed backward.
The energy transferred to the spring is given by:
where
k is the spring constant
x is the elongation of the spring with respect its initial length
Let's convert the data into the SI units:
so now we can use these data inside the equation ,to find the energy transferred to the spring:
