# Competitive Exams: Physics MCQs (Practice_Test 6 of 35)

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If more than three forces are acting on the massive point object, then the object will be in equilibrium if and only if all the forces are

collinear

coplanar

acting in random directions

represented by the sides of a closed polygon

A 10 kg mass is connected at one end of a massless spring with force constant k = 1000 N/m, keeping other end fixed in a horizontal plane as shown in the above figure. If the system is displaced by 0.01 m from its equilibrium position A to a point B, then the acceleration of the system is

10 ms-2

1 ms-2

-1 ms-2

-10 ms-2

A particle has two equal accelerations in two given directions. If one of the accelerations is halved, then the angle which the resultant makes with the other is also halves. The angle between the accelerations is

1200

900

600

450

A particle is projected at an elevation tan-1 (4/3) from a point O. The ratio of the range on the horizontal plane through O to the greatest height ascended above O is

2

3

4

5

The vertical height y and the horizontal distance x for a body projected in a vertical plane are given by y = 8t − 5t2 and x = 6t, then velocity with which body is projected is

6

5

8

10

A solid iron cylinder and sphere of the same material roll and slide respectively down an inclined plane in a frictionless manner. The kinetic energy of the cylinder at the bottom will be

equal to that of the sphere

more than that of the sphere

less than that of the sphere

more or less than that of sphere depending upon angle of the plane

The above figure shows the motion of a planet around the sun in an elliptical orbit with sun as the focus. The shaded areas A and B shown in the figure can be assumed to be equal. If t1 and t2 represent the times for the planet to move from ‘a’ to ‘b’ and ‘d’ to ‘c’ respectively, then

tl < t2

tl > t2

t1 = t2

None of the above

The escape velocity of a particle of mass m

varies as m 2

varies as m

varies as m − 1

is independent of mass

A body of mass 2 kg is hung on a spring balance mounted vertically in a lift. If the lift descends with an acceleration equal to the acceleration due to gravity ‘g’ then the reading on the spring balance will be

6 kg

4 kg

2 kg

zero

If R is the radius of the earth, p its mean density and G the gravitational constant, then the earth's surface potential will be nearly equal to

G/R2

(4/3) R3G

(4/3) R2G

(4/3) R/G

In an inelastic collision

momentum is conserved, but energy is not conserved

momentum is not conserved, but energy is conserved

neither momentum nor energy is conserved

both momentum and energy are conserved

If a is the coefficient of restitution, then which one of the following gives the condition for perfectly elastic bodies?

e = 0

e = 0.5

e = 0.8

e = 1.0

Viscosity is a transport phenomenon in which

mass alone is transported

energy alone is transported

mass and energy are transported

momentum is transported

Two soap bubbles A and B have radii rl and r2 respectively. If rl < r2, then the excess pressure inside

bubbles A and B will be equal

bubble A will be less than that in bubble B

bubble A will be greater than that in bubble B

bubbles A and B will be zero

Which one of the following represents the relativistic law of addition of velocities v1 and v2?