Question

a body of mass 1 kg is moving with velocity of ( 4i+3j ) m/s which changes to (-6i +2k ) m/s ,by a force .the work done by the force in changing the velocity is

a. 6 j
b. 10 j
c. 12.5 j
d. 7.5 j ​

Answer 1

HELLO DEAR,

QUESTION:- A body of mass 1 kg is moving with velocity of ( 4i+3j ) m/s which changes to (-6i +2k ) m/s ,by a force .the work done by the force in changing the velocity is

a. 6 j

b. 10 j

c. 12.5 j

d. 7.5 j

ANSWER:-

Given : A body of mass 1 kg is moving with velocity of ( 4i+3j ) m/s .

And it goes to change (-6i +2k ) m/s by a force.

To Find the work done by the force in changing the velocity of the body.

Solution:

Mass of body = 1 kg

Velocity of body = (4i+3j).

So, kinetic energy of body

KE = (1/2)mv²

= (1/2) (1) ( 4i+3j )^2

= (1/2) (1) ( 4i+3j ) (4i+3j)

= (1/2) (1) ( √(16+9)) (√16+9))

=(1/2) (1) ( 25

= 25/2

= 12.5

And finaly changes to (-6i +2k ) m/s.

KE = (1/2)mv²

= (1/2) (1) ( -6i+2j )^2

= (1/2)(1)(-6i+2j)(-6i+2j)

= (1/2) ( 36 + 4)

= (1/2)40

= 20

Work done by the force is change in kinetic energy = (20 - 12.5 ) = 7.5 Joule.

Option d. 7.5 j is correct .

I HOPE IT'S HELP YOU DEAR,

THANKS.