2 Blocks 1 and 2 rest on rough surfaces with coefficient of frictions ¢1 and ¢2 respectively. The blocks are connected by a cable that runs over a smooth pulley and are in equilibrium as shown below with the following values.

W2 = 50N
thetha 1 = 30 degrees
thetha 2= 40 degrees
¢1= 0.3
¢2= 0.25

a. If Block 2 is on the verge of sliding down the plane, what is the minimum weight W1, required for equilibrium?
b. If Block 2 is on the verge of sliding up the plane, what is the minimum weight W1, required for equilibrium
? Do not consider overturning.
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Explanation:

a) On the verge of tipping over, reaction acts at the corner A

When slippage occurs,

Block moves w/ const. velocity  equilibrium

Three-force member: reaction at A must pass through B

tan b/2h, h b/ 2 θ µ = = ∴= k k ( µ )

b) When slippage occurs,

Block moves w/ const. velocity  equilibrium

Three-force member: reaction at C must pass through G

k tanθ µ =

tan x/ H/2 , x H/2

energy can cross the boundaries of a closed system in the form of heat and mass

explanation:

the equation above shows how temperature f, measured in degrees fahrenheit, relates to a temperature c, measured in degrees celsius. based on the equation, which of the following must be true?

a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of

5

9

degree celsius.

a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit.

a temperature increase of

5

9

degree fahrenheit is equivalent to a temperature increase of 1 degree celsius.

a) i only

b) ii only

c) iii only

d) i and ii only