TU IOE | Physics
At a height equal to the radius of the Earth above its surface, the acceleration due to gravity is
Answer: $g/4$
Model set 1, Q40: explanation →A planet has 8 times the mass and 2 times the radius of the Earth. If the Earth's escape speed is 11.2 km/s, the escape speed from this planet is
Answer: 22.4 km/s
Model set 1, Q55: explanation →At a height equal to the Earth's radius above the surface, the acceleration due to gravity is
Answer: $\frac g4$
Model set 2, Q40: explanation →A planet has 8 times the mass and 2 times the radius of the Earth. If the Earth's escape velocity is 11.2 km/s, the planet's escape velocity is
Answer: 22.4 km/s
Model set 2, Q55: explanation →The moment of inertia of a uniform solid disc of mass $M$ and radius $R$ about its central axis perpendicular to its plane is
Answer: $\dfrac12MR^2$
Model set 1, Q41: explanation →A uniform disc of mass 2 kg and radius 0.5 m rotates about its axis at 10 rad/s. Its rotational kinetic energy is
Answer: 12.5 J
Model set 1, Q56: explanation →The moment of inertia of a uniform solid sphere of mass $M$ and radius $R$ about its diameter is
Answer: $\frac25MR^2$
Model set 2, Q37: explanation →A skater of moment of inertia $3\ \mathrm{kg,m^2}$ spins at 4 rad/s. On pulling in the arms the moment of inertia becomes $1.5\ \mathrm{kg,m^2}$. The final rotational kinetic energy is
Answer: 48 J
Model set 2, Q53: explanation →A car starting from rest accelerates uniformly at $2\ \text{m/s}^2$. The distance covered in 5 s is
Answer: 25 m
Model set 1, Q36: explanation →A ball is thrown vertically upward at 20 m/s ($g=10\ \text{m/s}^2$). The total distance it travels in the first 3 s is
Answer: 25 m
Model set 1, Q52: explanation →A ball is thrown vertically upward with a speed of 20 m/s. Taking $g=10\ \mathrm{m/s^2}$, the maximum height reached is
Answer: 20 m
Model set 2, Q36: explanation →A ball of mass 0.5 kg hits a wall at 4 m/s and rebounds at 4 m/s along the same line. The magnitude of the change in its momentum is
Answer: 4 kg m/s
Model set 1, Q37: explanation →Masses of 3 kg and 2 kg hang from the two ends of a light string over a smooth pulley ($g=10\ \text{m/s}^2$). The tension in the string is
Answer: 24 N
Model set 1, Q53: explanation →A block starts from rest on a smooth incline of $30^\circ$. Taking $g=10\ \mathrm{m/s^2}$, the distance it slides in 4 s is
Answer: 40 m
Model set 2, Q52: explanation →The gauge pressure at a depth of 10 m in water is about ($\rho=1000\ \text{kg/m}^3$, $g=10\ \text{m/s}^2$)
Answer: $10^5$ Pa
Model set 1, Q43: explanation →The gauge pressure at a depth of 5 m in water ($\rho=1000\ \mathrm{kg/m^3},\ g=10\ \mathrm{m/s^2}$) is
Answer: $5\times10^4$ Pa
Model set 2, Q38: explanation →Water flows at 2 m/s in a pipe of diameter 6 cm which narrows to a diameter of 3 cm (horizontal pipe). The pressure drop in the narrow section is ($\rho=1000\ \mathrm{kg/m^3}$)
Answer: $3\times10^4$ Pa
Model set 2, Q54: explanation →A straight rod of length 0.5 m moves at 4 m/s perpendicular to a uniform magnetic field of 0.2 T. The induced emf across its ends is
Answer: 0.4 V
Model set 1, Q49: explanation →The magnetic flux through a coil falls from 0.04 Wb to 0.01 Wb in 0.1 s. The magnitude of the induced emf is
Answer: 0.3 V
Model set 2, Q48: explanation →A rod 0.5 m long moves at 4 m/s perpendicular to a field of 0.3 T, sliding on rails that complete a circuit of resistance 2 ohm. The induced current is
Answer: 0.3 A
Model set 2, Q62: explanation →A pipe closed at one end is 0.5 m long. If the speed of sound is 340 m/s, its fundamental frequency is
Answer: 170 Hz
Model set 1, Q59: explanation →The fundamental frequency of a pipe closed at one end of length 0.5 m is (speed of sound 340 m/s)
Answer: 170 Hz
Model set 2, Q44: explanation →A string 0.8 m long fixed at both ends carries waves of speed 200 m/s. The frequency of its third harmonic is
Answer: 375 Hz
Model set 2, Q59: explanation →In a series RLC circuit, $R=30\ \Omega$, $X_L=60\ \Omega$ and $X_C=20\ \Omega$. The impedance is
Answer: 50
Model set 1, Q62: explanation →The rms value of an alternating voltage with a peak value of 100 V is about
Answer: 70.7 V
Model set 2, Q49: explanation →A series LCR circuit has $R=30\ \Omega$, $X_L=60\ \Omega$, $X_C=20\ \Omega$ and is connected to a 100 V rms supply. The rms current is
Answer: 2 A
Model set 2, Q61: explanation →The kinetic energy of a 2 kg body moving at 3 m/s is
Answer: 9 J
Model set 1, Q38: explanation →A 2 kg block slides from rest down a rough incline from a height of 5 m and reaches the bottom at 8 m/s ($g=10\ \text{m/s}^2$). The work done against friction is
Answer: 36 J
Model set 1, Q54: explanation →A wire stretches by $x$ under a load. A wire of the same material and cross-section but double the length, under the same load, stretches by
Answer:
Model set 1, Q42: explanation →A wire of length $L$ and radius $r$ is stretched by a force $F$. If both its length and radius are doubled, the extension for the same force becomes
Answer: half
Model set 2, Q39: explanation →The heat needed to raise the temperature of 2 kg of water by $10^\circ$C is ($c=4200\ \text{J kg}^{-1}\text{K}^{-1}$)
Answer: 84000 J
Model set 1, Q44: explanation →The heat needed to raise the temperature of 200 g of water from 20 degC to 50 degC is ($c=4200\ \mathrm{J,kg^{-1}K^{-1}}$)
Answer: 25200 J
Model set 2, Q41: explanation →A gas absorbs 200 J of heat and does 50 J of work. The change in its internal energy is
Answer: 150 J
Model set 1, Q45: explanation →Two moles of a monatomic ideal gas are heated at constant volume from 300 K to 400 K ($R=8.3\ \mathrm{J,mol^{-1}K^{-1}}$). The change in internal energy is
Answer: 2490 J
Model set 2, Q57: explanation →An object is placed 20 cm in front of a concave mirror of focal length 10 cm. The image is
Answer: real, at 20 cm in front of the mirror
Model set 1, Q46: explanation →An object is placed 30 cm from a concave mirror of focal length 20 cm. The image distance is
Answer: 60 cm
Model set 2, Q43: explanation →Two capacitors of 6 $\mu$F and 3 $\mu$F are connected in series. The equivalent capacitance is
Answer: 2 F
Model set 1, Q48: explanation →Capacitors of $6\ \mu$F and $3\ \mu$F are connected in series. The equivalent capacitance is
Answer: $2\ \mu$F
Model set 2, Q45: explanation →The energy of a photon of wavelength 620 nm is about (use $E=1240/\lambda$ eV with $\lambda$ in nm)
Answer: 2 eV
Model set 1, Q51: explanation →Light of photon energy 5 eV falls on a metal of work function 2 eV. The maximum kinetic energy of the emitted electrons is
Answer: 3 eV
Model set 2, Q51: explanation →A Carnot engine works between 400 K and 300 K and absorbs 1000 J from the source per cycle. The work done per cycle is
Answer: 250 J
Model set 1, Q57: explanation →The efficiency of a Carnot engine working between 500 K and 400 K is
Answer: 20%
Model set 2, Q42: explanation →In Young's double slit experiment, $\lambda=600$ nm, slit separation $d=1$ mm and screen distance $D=1$ m. The fringe width is
Answer: 0.6 mm
Model set 1, Q60: explanation →In Young's experiment the slit separation is 0.5 mm, the screen is 1 m away, and the wavelength is 500 nm. The distance of the 3rd bright fringe from the central maximum is
Answer: 3 mm
Model set 2, Q58: explanation →A radioactive sample of 80 g has a half-life of 10 days. The mass remaining after 30 days is
Answer: 10 g
Model set 1, Q63: explanation →A radioactive sample has a half-life of 10 days. The fraction remaining after 30 days is
Answer: $\frac18$
Model set 2, Q50: explanation →A particle moves in a circle of radius 5 m with a uniform speed of 10 m/s. Its centripetal acceleration is
Answer: $20\ \text{m/s}^2$
Model set 1, Q39: explanation →A wave of frequency 50 Hz has a wavelength of 4 m. Its speed is
Answer: 200 m/s
Model set 1, Q47: explanation →In an n-type semiconductor the majority charge carriers are
Answer: electrons
Model set 1, Q50: explanation →An object is placed 30 cm from a convex lens of focal length 20 cm. The image distance is
Answer: 60 cm
Model set 1, Q58: explanation →A cell of emf 10 V and internal resistance 1 $\Omega$ is connected to an external resistor of 4 $\Omega$. The terminal potential difference is
Answer: 8 V
Model set 1, Q61: explanation →A wire of resistance 10 ohm is stretched uniformly to double its length. Its new resistance is
Answer: 40 ohm
Model set 2, Q46: explanation →A straight wire 0.5 m long carrying 4 A is perpendicular to a field of 0.2 T. The force on it is
Answer: 0.4 N
Model set 2, Q47: explanation →A steel rod 2 m long at 20 degC is heated to 120 degC ($\alpha=1.2\times10^{-5}\ \mathrm{K^{-1}}$). The increase in length is
Answer: 2.4 mm
Model set 2, Q56: explanation →Two point charges, each $+4\ \mu$C, are 0.6 m apart in air. The electric potential at the midpoint is ($k=9\times10^9\ \mathrm{N,m^2C^{-2}}$)
Answer: $2.4\times10^5$ V
Model set 2, Q60: explanation →The mass defect of a helium-4 nucleus is 0.0304 u (1 u = 931.5 MeV). The binding energy per nucleon is about
Answer: 7.1 MeV
Model set 2, Q63: explanation →