Q.1- The number of significant figures in 0.06900 is:
Q.2- The numbers 2.745 and 2.735 on rounding off to 3 significant figures will give:
(a) 2.75 and 2.74
(b) 2.74 and 2.73
(c) 2.75 and 2.73
(d) 2.74 and 2.74
Q.3- A body covers half the distance with a speed of 20 m/s and the other half with a speed of 30 m/s. The average velocity of the body during the whole journey is:
(b) 24 m/s
(c) 25 m/s
(d) none of these
Q.4- The speed of a boat is 5 km/h in still water. It crosses a river of width 1 km along the shortest possible path in 15 min. The velocity of the river water is_____
(a) 1 km/h
(b) 3 km/h
(c) 4 km/h
(d) 5 km/h
Q.5- A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time the particle goes up is:
(a) -1.25 J
(b) 1.25 J
(c) 0.5 J
(d) - 0.5J
Q.6- A block of mass 50 kg slides over a horizontal distance of 1m. If the coefficient of friction between their surfaces is 0.2, then work done against friction is____
(a) 98 J
(b) 45 J
(c) 90 J
(d) 75 J
Q.7- When the force applied and the displacement of the body are inclined at 90° with each other, the work done is:
Q.8- When a body is in dynamic equilibrium, then work done is:
Q.9- The ratio between masses of two planets is 2:3 and the ratio between their radii is 3:2. Then the ratio between acceleration due to gravity on these two planets is:
Q.10- Velocity of sound in air is:
(a) faster in dry air than in moist air.
(b) directly proportional to pressure.
(c) directly proportional to temperature.
(d) independent of pressure of air.
Q.11- According to the kinetic theory of gases, at absolute temperature:
(a) water freezes.
(b) liquid helium freezes.
(c) molecular motion stops.
(d) liquid hydrogen freezes.
Q.12- A uniform metallic rod rotates about its perpendicular bisector with the constant angular speed. If it is heated uniformly to raise its temperature slightly:
(a) its speed of rotation increases.
(b) its speed of rotation decreases.
(c) its speed of rotation remains same.
(d) its speed increases because its moment of inertia increases.
Q.13- Heat is associated with:
(a) kinetic energy of random motion of molecules.
(b) kinetic energy of orderly motion of molecules.
(c) total kinetic energy of random and orderly motion of molecules.
(d) the kinetic energy of random motion in some cases and kinetic energy of orderly motion in others.
Q.14- For which of the following does the centre of mass lie outside the body?
(a) A pencil
(b) A shotput
(c) A dice
(d) A bangle
Q.15- A wire is suspended from the ceiling and stretched under the action of a weight F suspended from its other end. The force exerted by the celling on it is equal and opposite of the weight.
(a) Tensile stress at any cross section A of the wire is F/A.
(b) Tensile stress at any cross section is zero.
(c) Tension at any cross section A of the wire is F.
(d) Both a and c