7.5 I think because it can not be 9 because it’s not close to 50
        
             
        
        
        
Answer:

Explanation:
The total energy of the satellite when it is still in orbit is given by the formula

where
G is the gravitational constant
m = 525 kg is the mass of the satellite
 is the Earth's mass
 is the Earth's mass
r is the distance of the satellite from the Earth's center, so it is the sum of the Earth's radius and the altitude of the satellite:

So the initial total energy is

When the satellite hits the ground, it is now on Earth's surface, so

so its gravitational potential energy is

And since it hits the ground with speed

it also has kinetic energy:

So the total energy when the satellite hits the ground is

So the energy transformed into internal energy due to air friction is the difference between the total initial energy and the total final energy of the satellite:

 
        
             
        
        
        
Explanation:
First, we need to determine the distance traveled by the car in the first 30 minutes,  .
.
Notice that the unit measurement for speed, in this case, is km/hr. Thus, a unit conversion of from minutes into hours is required before proceeding with the calculation, as shown below
                                           
Now, it is known that the car traveled 40 km for the first 30 minutes. Hence, the remaining distance,  , in which the driver reduces the speed to 40km/hr is
 , in which the driver reduces the speed to 40km/hr is
                                               .
.
Subsequently, we would also like to know the time taken for the car to reach its destination, denoted by   .
.
                                                .
.
Finally, with all the required values at hand, the average speed of the car for the entire trip is calculated as the ratio of the change in distance over the change in time.
                                                      
Therefore, the average speed of the car is 50 km/hr.
 
        
             
        
        
        
Answer:
Explanation:
You could try to say how helpful they are what they are and what they do