Answer:
The speed of the cart decreases
Explanation:
The track is frictionless, so we can consider the cart as isolated system (no external forces acting on it): therefore, the momentum of the cart is conserved
where m is the mass and v the speed of the cart.
When it starts raining, some water falls into the cart: this means that the mass of the cart, m, increases. But we said that the momentum, p, must remain constant: in order for that to happen, this means that the speed of the cart, v, must decrease (because the relationship 
is an inverse relationship, so if m increases, v must decrease).
Answer:
60 Ω
Explanation:
R(com) = 15 Ω
1/R(com) = 1/R1 + 1/R2 + 1/R3 ..... + 1/Rn
1/15 = 1/20 + 1/R2
1/R2 = 1/15 - 1/20
1/R2 = (4 - 3) / 60
1/R2 = 1/60
R2 = 60 Ω
así, la combinada de resistencia necesaria es 60 Ω
At the time that I'll call ' Q ', the height of the stone that was
dropped from the tower is
H = 50 - (1/2 G Q²) ,
and the height of the stone that was tossed straight up
from the ground is
H = 20Q - (1/2 G Q²) .
The stones meet when them's heights are equal,
so that's the time when
<span>50 - (1/2 G Q²) = 20Q - (1/2 G Q²) .
This is looking like it's going to be easy.
Add </span><span>(1/2 G Q²) to each side.
Then it says
50 = 20Q
Divide each side by 20: 2.5 = Q .
And there we are. The stones pass each other
2.5 seconds
after they are simultaneously launched.
</span>
Answer: a) 0.13*τ ; b) 2.08*τ
Explanation: In order to explain the discharg of a capacitor through a resistor, we have to consider the following:
Q(t)=Qo* exp(-t/τ) for a lose of 1/8-th of its charge
in this case, Q(t)=7/8*Qo=7/8*exp(-t/τ)
ln(7/8)*τ=-t
then, t= -ln(7/8)*τ =0.13
For a lose of 7/8 th of its charge , we have
Q(t)=1/7*Qo*exp(-t/τ)
t=-ln(1/8)*τ=2.08
Its the amount of matter in something.
for example, a large truck as compared to a mouse, the truck would have much greater of a mass.
