Question

1.
A uniform horizontal beam, pivoted at its right-hand end, is in equilibrium. A force of 60 N
acts vertically upwards on the beam as shown.
60N
ㅏ ma
60 =
20 cm
30 cm
pivot
weight
of beam
What is the weight of the beam?
(A) 36 N.
(B) 90 N
(C) 40 N
(D) 100 N​

Answer 1

Answer:

I think (a) 36 N. Is right I was thinking

Answer 2

Answer:

VIDEO EXPLANATION

ANSWER

When the rod rotates through an angle θ, the centre of gravity falls through a distance h. From ΔBCG

′

cosθ=

μ

2

(1/2)−h

h=

2

l

(1−cosθ)

Decrease in PE

=mg

2

l

(1−cosθ) ....(i)

The decrease in P.E. is equal to the kinetic energy of rotation (

2

1

Iω

2

)

(KE)

rotational

=

2

1

(

3

ml

2

)ω

2

.....(ii)

From Eqs. (i) and (ii), we get

2

1

(

3

ml

2

)ω

2

=mg

2

l

(1−cosθ)

ω=

l

6g

sin

2

θ

.

solution

Answer By

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Toppr