Answer:
The density will be 0.65 kg/m3 
I think it won't float!! I am not sure though. 
 
        
             
        
        
        
Velocity includes direction, for instance going 140 MPH is speed but going 140 MPH North is velocity
        
                    
             
        
        
        
Option B makes best sense, correct me if i’m wrong
        
             
        
        
        
Explanation:
By Hooke's Law,
F=kx
The only force acting here is weight, and x is the extension of the string (you need to convert this to mm) so
mg=kx
(0.15)(9.81)=k ((420-300)x10^-3)
Then just solve this equation.
 
        
             
        
        
        
Answer:
Work done = -220,000 Joules. 
Explanation:
<u>Given the following data;</u>
Mass = 1100kg
Initial velocity = 20m/s
To find workdone, we would calculate the kinetic energy possessed by the car. 
Kinetic energy can be defined as an energy possessed by an object or body due to its motion. 
Mathematically, kinetic energy is given by the formula;

Where,
- K.E represents kinetic energy measured in Joules. 
- M represents mass measured in kilograms. 
- V represents velocity measured in metres per seconds square. 
Substituting into the equation, we have;
 
 
 
 
K.E = 220,000J
Therefore, the workdone to bring the car to rest would be -220,000 Joules because the braking force is working to oppose the motion of the car.