ISRO Scientist or Engineer Mechanical 2007

Instructions

For the following questions answer them individually

Question 71

A heavy block of mass m is slowly placed on a conveyer belt moving with speedv.If coefficient of friction between block and the belt is $$\mu$$, the plock will slide on the pert through distance

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Question 72

A car moving with uniform acceleration covers 450 m in a 5 second interval, and covers 700 m in the next 5 second interval. The acceleration of the car is

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Question 73

A particle starts with a velocity 2m/sec and movesona straight-line track with retardation 0.1 m/sec$$^2$$. The time at which the particle is 15 m from the starting point would be

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Question 74

Two particles with massesin the ratio 1 : 4 are moving with equal kinetic energies. The magnitudeof their linear momentums will conform to the ratio

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Question 75

A stone is projected horizontally from a cliff at 10 m/sec and lands on the ground belowat 20 m, from the baseofthe cliff. Find the height of the cliff. Use g = 10 m/sec$$^2$$ ?

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Question 76

Oscillation of a particle is prescribed by the equation $$x = 3 \cos 0.25 \pi t$$ Wheret is the time in seconds.
Then time taken by the particle to move from position of equilibrium to maximum displacement is

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Question 77

Which of the following is not a scalar quantity

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Question 78

Which of the following stresses are associated with the tightening of a nut on a stud?
1. Tensile stresses due to stretching of stud.
2. Bending stresses of stud.
3. Transverse shear stresses acrossthreads. .
4. Torsional shear stresses in threads due tofrictional resistance.
Select the correct answer using the codes given below Codes:

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Question 79

A thin copper wire at $$300^\circ$$ is suddenly immersed in water at $$30^\circ C$$. It cools down to $$150^\circ C$$ in 70 seconds. It is then reheated to the initial temperature of $$300^\circ C$$ and suddenly exposedto air at $$30^\circ C$$ where it cools downto $$150^\circ C$$ in 200 seconds. This difference in cooling time is due to

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Question 80

The heat flow rate through parallel walls of thickness $$L_1, L_2$$ and $$L_3$$, having surface areas $$A_1, A_2$$ and $$A_3$$, thermal conductivities $$k_1, k_2$$ and $$k_3$$,
respectively, with the first and last walls maintained at temperatures $$t_1$$ and $$t_2$$ will be

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