Answer:
a)Velocity of car =v=16 m/s
b)Force against the track at point B=1.15* N
N 
Explanation:
Given mass of roller coaster=m=350 kg
Position of A=Ha=25 m
Position of B=Hb=12 m
Net potential energy=mg(ha-hb)
Net potential energy=(350)(9.80)(25-12)
Net potential energy=44590 J
Using energy conservation
net kinetic energy=net potential energy
(1/2)mv^2=mg(ha-hb)
m=350
velocity=v=16 m/s
b)There two force acting,centripetal force upward and gravity downward.
Thus net force acting will be 
Net force=(mv^2/r)-mg
Net force=14933.33-3430
Net force=1.15* N
 N
 
        
                    
             
        
        
        
 <span>If the refrigerator weights 1365 and you are not exerting any vertical force on it, then the normal force is also 1365N. so Fn=1365 
Fsf = Static frictional force = (coefficient of static friction) * (Normal force) 
So the least for you could exert to move it is equal to the Fsf. 
Fsf = (0.49)(1365N)</span><span>
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Answer:
 v = 2,425 m / s
Explanation:
A simple pendulum has anergy stored at the highest point of the path and this energy is conserved throughout the movement.
highest point
            Em₀ = U = m g y
lowest point
            = K = ½ m v²
 = K = ½ m v²
          Em₀ = Em_{f}
         mg y = ½ m v²
         v = √ 2gy
let's calculate
         v = √ (2 9.8 0.3)
         v = 2,425 m / s
 
        
             
        
        
        
The ozone layer that is inside the stratosphere blocks UV radiation.
The ozone layer contains high concentrations of ozone relative to other parts of the atmosphere. This was discovered by Charles Fabry and Henri Buisson who are both French Physicists. 
The ozone in the earth's stratosphere is created through ultraviolet light striking a group of ordinary oxygen molecules containing two oxygen atoms, subsequently splitting them into individual oxygen atoms and finally these said atomic oxygen then combines with unbroken O2 to create ozone (O3).