D. Free fall
Explanation:
An object is said to be in free fall when there is only one force acting on the body, which is the force of gravity.
Near the Earth's surface, the force of gravity acting on a body is given by
F = mg
where
m is the mass of the body
g is the acceleration of gravity (its value is
)
The direction of this force is downward (towards the Earth's centre).
If we apply Newton's second law on an object in free-fall, we can find its acceleration. In fact, we have:

And substituting F,

So, every object in free-fall accelerates at
towards the ground.
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Answer:
3.9 m/s
Explanation:
We are given that
Mass of car,m=
Initial velocity,u=0
Distance,s=5.9 m

Average friction force,f=
We have to find the speed of the car at the bottom of the driveway.
Net force,
Where 
Acceleration,


v=3.9 m/s
Answer:
aaksj
Explanation:
a) the capacitance is given of a plate capacitor is given by:
C = \epsilon_0*(A/d)
Where \epsilon_0 is a constant that represents the insulator between the plates (in this case air, \epsilon_0 = 8.84*10^(-12) F/m), A is the plate's area and d is the distance between the plates. So we have:
The plates are squares so their area is given by:
A = L^2 = 0.19^2 = 0.0361 m^2
C = 8.84*10^(-12)*(0.0361/0.0077) = 8.84*10^(-12) * 4.6883 = 41.444*10^(-12) F
b) The charge on the plates is given by the product of the capacitance by the voltage applied to it:
Q = C*V = 41.444*10^(-12)*120 = 4973.361 * 10^(-12) C = 4.973 * 10^(-9) C
c) The electric field on a capacitor is given by:
E = Q/(A*\epsilon_0) = [4.973*10^(-9)]/[0.0361*8.84*10^(-12)]
E = [4.973*10^(-9)]/[0.3191*10^(-12)] = 15.58*10^(3) V/m
d) The energy stored on the capacitor is given by:
W = 0.5*(C*V^2) = 0.5*[41.444*10^(-12) * (120)^2] = 298396.8*10^(-12) = 0.298 * 10 ^6 J
The acceleration of the car will be needed in order to calculate the time. It is important to consider that the final speed is equal to zero:

We can clear time in the speed equation:

If you find some mistake in my English, please tell me know.
Answer:
In an elastic collision, the momentum is conserved and the mechanical energy is conserved too.
Explanation:
There are two types of collisions:
- Elastic collision: in an elastic collision, the total momentum before and after the collision is conserved; also, the total mechanical energy before and after the collision is conserved.
- Inelastic collision: in an inelastic collision, the total momentum before and after the colllision is conserved, while the total mechanical energy is not conserved (in fact, part of the energy is converted into other forms of energy such that thermal energy, due to the presence of frictional forces)