Answer:
4. It is the force of the road on the tires (an external force) that stops the car.
Explanation:
If there is no friction between the road and the tires, the car won't stop.
You can see this, for example, when there is ice on the road. You can still apply the brakes (internal force), but since there is no friction (external force) the car won't stop.
The force of the brakes on the wheels is not what makes the car stop, it is the friction of the road against still tires that makes it stop.
 
        
             
        
        
        
Hello!
Recall the period of an orbit is how long it takes the satellite to make a complete orbit around the earth. Essentially, this is the same as 'time' in the distance = speed * time equation. For an orbit, we can define these quantities: 
 ← The circumference of the orbit
 ← The circumference of the orbit 
speed = orbital speed, we will solve for this later
time = period 
Therefore: 

Where 'r' is the orbital radius of the satellite. 
First, let's solve for 'v' assuming a uniform orbit using the equation:

G = Gravitational Constant (6.67 × 10⁻¹¹ Nm²/kg²) 
m = mass of the earth (5.98 × 10²⁴ kg) 
r = radius of orbit (1.276 × 10⁷ m) 
Plug in the givens:

Now, we can solve for the period: 

 
        
             
        
        
        
High frequency , it is because wavelength is inversely proportional to frequency
        
             
        
        
        
Answer
b. the number of atoms in each molecule.
Explanation: