D FOUR years old hope this helps
mark brainliest please
 
        
                    
             
        
        
        
Answer:
Please find the answer in the explanation 
Explanation:
Friction is a force that opposes motion. One or two of the advantages of friction are break and ability of an object to walk.
Writing yes it is useful because when your writing because friction helps you see what your writing 
ii. Rubbing. Yes, it is useful. 
friction make it possible for two object to rub each other 
 iii. Skiing. No. It is not useful because With presence of friction, skiing will not be possible. 
 iv. Rotating a wheel No. It is not useful because Friction will oppose the rotation of the wheel. 
 
        
             
        
        
        
The final temperature of the tea cup is 100°C.
<h3>What is internal energy?</h3>
The Internal energy is the energy of a substance due to to the constant random motion of its particles.
The symbol for internal energy of a substance is U and it is measured in Joules.
ΔU = q + W
- W is the mechanical work.
In conclusion,  the final temperature of the tea cup at room temperature of 24 °C which is heated until it has twice the internal energy is 100°C.
Learn more about internal energy at: brainly.com/question/24028630
#SPJ1
 
        
             
        
        
        
Answer:
Torque = R X F = R * F sin theta
-f * 2R  will exert an equal opposite torque
-f * 2 = F sin theta
f = -F sin theta / 2
 
        
             
        
        
        
More force needs to be applied