  # 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 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 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 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 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$$^2$$ ? 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 Question 77

# Which of the following is not a scalar quantity 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: 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 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 OR