The number of significant figures in the numbers 4.8000 x 10⁴ and 48000.50 are respectively

• 5 and 6

• 5 and 7

• 2 and 7

• 2 and 6

A body of mass m moving along a straight line covers half the distance with a speed of 2ms^-1. The remaining half of the distance is covered in two equal time intervals with a speed of 3 ms^-1 and 5 ms^-1 respectively. The average speed of the particle for the entire journey is

• $\frac{3}{8} {\mathrm{ms}}^{-1}$

• $\frac{8}{3} {\mathrm{ms}}^{-1}$

• $\frac{4}{3} {\mathrm{ms}}^{-1}$

• $\frac{16}{3} {\mathrm{ms}}^{-1}$

The moment of inertia ofa circular ring of radius r and mass M about diameteris

• $\frac{2}{5} {\mathrm{Mr}}^2$

• $\frac{{\mathrm{Mr}}^2}{4}$

• $\frac{{\mathrm{Mr}}^2}{2}$

• $\frac{{\mathrm{Mr}}^2}{12}$

4.

A body of mass 0.05 kg is observed to fall with an acceleration of 9.5 ms^-2. The opposing force of air on the body is (g = 9.8 ms^-2)

• 0.015 N

• 0.15 N

• 0.030 N

• zero

Three concurrent co-planar forces 1 N, 2 N and 3 N acting along different directions on a body

• can keep the body in equilibrium if 2 N and 3 N act at right angle

• can keep the body in equilibrium if 1 N and 2 N act at right angle

• cannot keep the body in equilibrium

• can keep the body in equilibrium in 1 N and 3 N act at an acute angle

Two rectangular blocks A and B of masses 2 kg and 3 kg respectively are connected by a spring of spring constant 10.8 Nm^-1 and are placed on a frictionless horizontal surface. The block A was given an initial velocity of 0.15 ms^-1. in the direction shown in the figure. The maximum compression of the spring during the motion is

• 0.01 m

• 0.02 m

• 0.05 m

• 0.03 m

The work done by a force acting on a body is as shown in the graph. The total work done in covering an initial distance of 20 m is

• 225 J

• 200 J

• 400 J

• 175 J

A door 1.6 m wide requires a force of 1 N to be applied at the free end to open or close it. The force that is required at a point 0.4 m distance from the hinges for opening or closing the door is

• 1.2 N

• 3.6 N

• 2.4 N

• 4 N

A planet revolves around the sun in an elliptical orbit. The linear speed of the planet will be maximum at

• D

• B

• A

• C

Two sources are said to be coherent if they produce waves

• having a constant phase difference

• of equal wavelength

• of equal speed

• having same shape of wavefront