Nine Standard >> Numerical problems from work, power & energy

Numerical problems from work, power & energy

Q1. On the application of 50 N force, if the work is done 600 J. What will be the displacement of the point of application of force?

Solve:

     W=F \(\times\) d

         W=work=600 J
         F=force=50 N
         d=displacement=?

    600=50 \(\times\) d
\(\therefore\) d=\(\frac{600}{50}\)
                        =12 m 

Q2. A body of mass 50 kg acquires 400 J of kinetic energy. Find the velocity of the body.

Solve:
   
    \(E_k\)=\(\frac{1}{2}mv^{2}\)
          
          \(E_k\)=kinetic energy=400 J
          m=mass of the body=50 kg

     400=\(\frac{1}{2} \times m \times v^{2}\)
or, 400=\(25 v^{2}\)
or, \(v^{2}\)=\(\frac{400}{25}\)=16
\(\therefore\) v=\(\pm\sqrt{16}\)
or v=\(\pm 4\) m/s
\(\therefore\) v=4 m/s

Q3. A stone of mass 100 kg was lifted to a height of 10 m. Find the potential energy, possessed by the body. (g=9.8 m/\(s^{2}\))

Solve:

 \(E_p\)=mgh
     
    m= mass of the stone=100 kg 
    h= height=10 m
    g= gravitational force=9.8 m/\(s^{2}\) 
    \(E_p\)=potential energy=?  

\(E_p\)=100 \(\times\) 9.8 \(\times\) 10
         =9800.0
         =9800 J