Question

a block of metal weighing 2 kg is resting on a frictionless plane it is struk by jet releasing water and a wieght 1 kg s^-1 and speed at a rate of 5 ms^-1 the initial acceleration is

Answer 1

The final velocity of mass of water after hitting the metal block is zero.

So the average change in momentum per sec = initial momentum  

=

mass

×

initial velocity of water

=

1

k

g

×

5

m

/s

=

5

k

g

m

/s

As this change in momentum occurs during 1 sec. We may say that the force exerted on the 2kg metal block is

F

=

change in momentum

time

=

5

k

g

m

/s

1

s

=

5

N

Hence by Newton's law initial acceleration of the block of mass  

m

=

2

k

g

is given by

a

=

F

m

=

5

N

2

k

g

=

2.5

m

/

s

2

Answer 2

Answer :-

F = v dm/dt

= 5 x 1

= 5N

acceleration= a = F/m

= 5/2

= 2.5 ms⁻²