Dynamics

1.A force of 20N moves a body with an acceleration of 2ms^-2

what is the mass ?

Given Data

                

                 F = 20N

                 a = 2ms^-1

To find

                   m = ?

Formula

                 F = ma  or  m = F/a

Calculation

As

           m = F/a

putting the values we get

            m = 20/2   =  10kg

Hence the body having mass of 10kg.

2.The weight to a body is 147N. What is the mass?(take value of g as 10ms^-2).

Given Data

                  w = 147N

                   g = 10ms^-2

To Find

                        m = ?

Formula

                  w = mg or   m =w/g

Calculation

as

              m  = w/g

putting the values

              m = 147/10

              m = 14.7kg

Hence the body having mass of 14.7kg.

3.How much force is needed to prevent a body of mass 10kg from falling?

Given Data

                 Mass = m  = 10kg

                 Gr.acceleration = 10ms^-2

To Find

              F = w = ?  

Formula

                   F = w = mg    

Calculation

                   w = 10 × 10 N

                    w = 100N

  

 Hence 100N force will required!

4.Find the acceleration produce by a force of 100N in a mass of 50kg?

Given Data

                     Force = F =100N

                     mass = m =50kg  

To Find

                   acceleration = a = ? 

Formula

                    F = ma     or      a = F/m 

Calculation

                          a = F/m

By Putting the values

a = 100/50     = 2ms^-2

Hence acceleration will be 2ms^-2.

5.A body ha s weight 20N. How much force is required to move it vertically upwards with an acceleration of 20ms^-2?

Given Data

weight = w = 20N

acceleration = a = 2ms^-2

To Find

Force for upward motion = F_up = ? 

Formula

m = w/g

F = ma

Total Force = F_up = F + w

Calculation

First of all we have to find mass so,

                    m  = w/g = 20/10 = 2kg

Now we have to find force which create acceleration “a”

F = ma = 2 × 2N

Now finally we have to find the total upthrust

F_up = F + w = 4 + 20 = 24N

Henc total force will 24N.

6. Two masses 52kg and 48kg are attached to the ends of a string that passes 

over a frictionless pulley. Find the tension in the string and acceleration 

in the bodies when both the masses moving vertically.

Given Data

mass of first body = m₁ = 52kg

mass of first body = m₁ = 48kg

To Find

Tension in string = T = ?

acceleration = a = ?

Formula

Calculation

7.Two masses 26kg and 24kg are attached to both ends of a string which passes over a friction less pulley. 26kg is lying over a smooth horizontal table. 24kg is moving vertically downward. Find the tension in the string and the acceleration in the bodies?

Given Data

mass of first body = m₁ = 24kg

mass of first body = m₁ = 26kg

To Find

Tension in string = T = ?

acceleration = a = ?

Formula

Calculation

8.How much time is required to change 22Ns momentum by a force of 20N ?

Given Data

           Change in momentum = ∆P = 22Ns

           Force = F = 20N 

To Find

              time = t =?

Formula

        Force = change in momentum/time

        F = ∆P/t

Calculation

as

             F = ∆P/t        or      t = ∆P/F       

By putting the values

            t = 22/20

            t = 1.1s

Hence time will be “1.1s”

9.How much is the force of friction between wooden block of mass 5kg 

and the Horizontal marble floor? The coefficient of friction  between 

wood and the marble is 0.6.

Given Data

                       mass = m = 5kg

                      Coefficient of friction = µ =0.6

To Find

                      F  = ?

Formula

                     F = µF_n = µmg

Calculation

                             as

                                      F = µmg

                            By putting the values

                                      F = 0.6 × 5 × 10 =30N

                                       Hence 30N force will require!

10. How much centripetal force is needed to make a body of mass 0.5kg to movie

 in a circle of radius 50 cm with a speed 3ms^-1?

Given Data

                           mass = m = 0.5kg

                          radius = r = 50cm = 0.5m

                          speed = v = 3ms^-1

To Find

                            Centripetal force = F_c = ?

Formula

                                F_c = mv²/r

Calculation

                                   as

                                             F_c = mv²/r

                                  Putting the values

                                            F_c = (0.5)(3)²/0.5

                                            F_c = (3)² = 9N

                                 Hence the force will be “9N”