Question

calculate change in momentum of the body. formula change in momentum =m(v_u)​

Answer 1

Answer:

There are two possible ways depending on the problem.

1) The change in momentum of an object is its mass times the change in its velocity.

Δ

p

=

m

⋅

(

Δ

v

)

=

m

⋅

(

v

f

−

v

i

)

.

v

f

and

v

i

are the final and initial velocities. Remember to use the right signs when substituting

v

f

and

v

i

Example) A 3kg mass initially moving 4m/s to the right rebounds off of a wall and begins travelling to the left at 2m/s.

Taking "right" to be the positive direction:

v

i

=+4m/s,

v

f

= –2m/s, and m=3kg. Substituting,

Δ

p

=

3

k

g

⋅

(

−

2

m/s

−

4

m/s)

=

−

18

kg m/s

2) The change in the momentum of an object can also be found by considering the force acting on it. If a force,

F

, acts on an object for a time,

Δ

t

, the change in the objects momentum is

Δ

p

=

F

⋅

Δ

t

.

Remember to use the right sign when substituting

F

. For example, a force to the left could be negative.

Lastly, if your object is moving both horizontally and vertically then

Δ

p

has a vertical and horizontal component. If this is the case, the above equations still work for each component separately, Ex) To find the horizontal component of

Δ

p

use the horizontal component of

v

i

,

v

f

or

F

in the above equations.