Hot air rises<span> because when you </span>heat air<span> (or any other gas for that matter), it expands. When the </span>air<span> expands, it becomes less dense than the </span>air<span>around it. The less dense </span>hot air<span> then floats in the more dense cold </span>air<span> much like wood floats on water because wood is less dense than water.</span>
Answer:
The speed after being pulled is 2.4123m/s
Explanation:
The work realize by the tension and the friction is equal to the change in the kinetic energy, so:
(1)
Where:

Because the work made by any force is equal to the multiplication of the force, the displacement and the cosine of the angle between them.
Additionally, the kinetic energy is equal to
, so if the initial velocity
is equal to zero, the initial kinetic energy
is equal to zero.
Then, replacing the values on the equation and solving for
, we get:


So, the speed after being pulled 3.2m is 2.4123 m/s
Answer:
light doesn't need a medium through which to travel because the speed of light is experimentally constant
Answer:
The speed is
and the direction is heading north.
Explanation:
In collisions the force exerted by the objects that collide is higher enough than the external forces that we can neglect that external forces, with that assumption we can use the conservation fo momentum law that states, final total momentum (pf) is equal initial total momentum (pi) if there’re not external forces or they are small enough to be neglected. Mathematically:

The total momentum is the sum of the momentum of each of the bodies we're dealing, in our case the moment of each car, then:

with pn the momentum of the 1000kg car heading north and ps the 800kg car heading south. Momentum is defined as mass times velocity, then:
(1)
It's important to note that when we talk about momentum and velocity direction matters, so we're are going to choose a system of reference where quantities pointing north are positive and pointing south are negative. So, the initial velocity of 1000 kg car is vni=5 m/s, initial velocity of 800 kg car is vsi=-4 m/s and the final velocity of 1000 kg car is vnf=-1 m/s. Now we can solve (1) for vsf and use the values we already have:

Because the sign is positive the direction is to heading north.