Two rods of negligible weight are pinned at b and attached to blocks a and c. find the value of p for impending motion and determine which block will move first, given: ma = 24 kg, mc = 60 kg, θ = 70 °, φ = 50 °, α = 35 °, μ = 0.25

N

Block A will move first

Explanation:

Let's call:

- the Force applied from A to B

- the Force applied from C to B

- the Force applied by P

Since the directions of all Forces above are towards B:

Angles between and  is °

Angles between and  is °

Angles between and is 180 - 85 - 20 = 75°

From Sine's Law:

For Block A, from Newton's Law:

⇒

⇒ where

Since

Then ⇒ N

For Block B, from Newton's Law:

⇒

⇒ where

Since

Then ⇒ N

Hence,

Since the value of P is smaller for Block A than Block B, Block A will move first.

And the required value of P is smaller one among the above, N

the answer is b, have negligible mass