Question

A body of mass 5 kg moving on a horizontal surface with a velocity of 10 m/s
comes to rest in 2s. The force required to make this body move with a velocity c
10 mis on the same surface is​

Answer 1

Given :

• Mass of body, m = 5 kg
• Initial velocity of body, u = 10 m/s
• Time after which body comes to rest, t = 2 s
• Final velocity of body, v = 0

To find :

• Force required to make the body move with same velocity of 10 m/s; F =?

Formula required :

• First equation of motion

      v = u + a t

• Expression for Newton's second Law of motion

    F = m a

[ Where F is force applied, m is mass, a is acceleration, v is final velocity, u is initial velocity and t is time ]

Solution :

Calculating the acceleration of the body (a =?)

Using first equation of motion

→ v = u + a t

→ 0 = ( 10 ) + a ( 2 )

→ -10 = 2 a

→ a = -5 m/s²

Calculating the force required on the body to keep in moving with 10 m/s (F =?)

[ Since, we need to make the body moving with same velocity (that is equal to initial velocity) therefore, acceleration required on applying force must be equal in magnitude to the deceleration of body on coming to rest after 2 sec. ]

Using Newton's second law's equation

→ F = m a

→ F = ( 5 ) ( 5 )

→ F = 25 N

Therefore,

• Force required on the body is equal to 25 Newton .