Question

A cube of mass m and side a is
moving along a plane with constant
speed vo
as shown in figure. The
magnitude of angular momentum of the
cube about 2-axis would be :-​

Answer 1

Explanation:

When the block hits the ridge O, it will start rotating about an axis passing through O and perpendicular to the plane of the paper

Net torque about O is zero,

Therefore, angular momentum L about O will be conserved.

L

i

=L

f

∴Mv(

2

a

)=I

O

ω=(I

cm

+Mr

2

)ω=(

6

Ma

2

+M(

2

a

)

2

)ω=

3

2

Ma

2

ω

where I

O

is the MI of the cube about point O and ω is the angular speed of rotation of the block about O.

∴ω=

4a

3v

Note: The MI of the square plate is

6

Ma

2

. Hence, MI of a cube will be also

6

Ma

2

solution