In order to ensure self locking in a screw jack, it is essential that helix angle is __________ friction angle.

In a screw jack, the effort required to lift the load W is given by (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction)

A

$${\text{P}} = {\text{W}}\tan \left( {\alpha - \varphi } \right)$$

B

$${\text{P}} = {\text{W}}\tan \left( {\alpha + \varphi } \right)$$

C

$${\text{P}} = {\text{W}}\tan \left( {\varphi - \alpha } \right)$$

D

$${\text{P}} = {\text{W}}\cos \left( {\alpha + \varphi } \right)$$

The efficiency of a screw jack is maximum, when (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction)

A

$$\alpha = {45^ \circ } + \frac{\varphi }{2}$$

B

$$\alpha = {45^ \circ } - \frac{\varphi }{2}$$

C

$$\alpha = {90^ \circ } + \varphi $$

D

$$\alpha = {90^ \circ } - \varphi $$

The efficiency of a screw jack is maximum, when (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction.)

A

$$\alpha = {45^ \circ } + \frac{\varphi }{2}$$

B

$$\alpha = {45^ \circ } - \frac{\varphi }{2}$$

C

$$\alpha = {90^ \circ } + \varphi $$

D

$$\alpha = {90^ \circ } - \varphi $$

Efficiency of a screw jack is given by (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction.)

A

$$\frac{{\tan \left( {\alpha + \varphi } \right)}}{{\tan \alpha }}$$

B

$$\frac{{\tan \alpha }}{{\tan \left( {\alpha + \varphi } \right)}}$$

C

$$\frac{{\tan \left( {\alpha - \varphi } \right)}}{{\tan \alpha }}$$

D

None of these

In a screw jack, the effort required to lift the load is given by (where W = Load lifted, α = Helix angle, and φ = Angle of friction.)

A

P = W tan (α - φ)

B

P = W tan (α + φ)

C

P = W tan (φ - α)

D

P = W cos (α + φ)

While designing a screw in a screw jack against buckling failure, the end conditions for the screw are taken as

A

both ends fixed

B

both ends hinged

C

one end fixed and other end hinged

D

one end fixed and other end free.

A screw is said to be a self locking screw, if its efficiency is

A

Less than 50%

B

More than 50%

C

Equal to 50%

D

None of these

A locking device in which the bottom cylindrical portion is recessed to receive the tip of the locking set screw, is called

A

Ring nut

B

Castle nut

C

Sawn nut

D

Jam nut

John, Jack, Joseph and Jordan participated in a running race. Only the winner finished the race in 10 minutes. Which two pieces of information can tell you who the winner was? (i) John finished the race in 16 minutes . (ii) Joseph finished the race earlier than Jack by 2 minutes. (iii) Jack finished the race later than Jordan by 4 minutes. (iv) Jordan finished the race earlier than John by 6 minutes. (v) John finished the race later than Joseph by minutes.

A

I and II

B

I and IV

C

II and III

D

II and V

When the screw in a mechanical screw jack rotates, the load kept on the top of it moves

A

Axially upwards

B

Axially downwards

C

Axially upwards or downwards

D

None of these

In order to ensure self locking in a screw jack, it is essential that helix angle is __________ friction angle.

Related Questions