Question

Mishka rolls some marbles on the floor. She observes that after travelling some distance,
the marbles finally stop. The marbles stopped because
(a) of the gravitational force exerted by the earth.
(b) the force applied was very less.
(c) of the frictional force between the marbles and the ground.
(d) the magnetic force between the ground and the marbles.

Answer 1

Answer:

option c) frictional force between the marble and the groud.

Answer 2

Answer:

option c) frictional force between the marble and the ground.

Explanation:

impulse=FΔt=mΔv

                so we have to find the velocity with which ball strikes the ground : v

1

​

=

2gh

​

=

2×10×20

​

=20

s

m

​

and for finding speed with which it rebounds such that it goes to a height of 5m will be                  

                                 v

2

​

=

2gh

​

=

2×10×5

​

=10

s

m

​

so, impulse=m(v

2

​

−v

1

​

)=0.10×(20−10)=1N−s

                     F=

dt

dP

​

=1/0.01=100N

Rough surfaces have more microscopic hills and valleys than smooth surfaces do. So, the rougher the surface is, the greater the friction is. ... The amount of kinetic friction between two surfaces depends in part on how the surfaces move. Surfaces can slide past each other, or a surface can roll over another surface.