A mass is supported on a frictionless horizontal surface. It is attached to a string and rotates about a fixed centre at an angular velocity ω₀. If the length of the string and angular velocity are doubled, the tension in the string which was initially T₀ is now 

(1) T₀

(2) T₀/2

(3) 4 T₀

(4) 8 T₀

An object with a mass 10 kg moves at a constant velocity of 10 m/sec. A constant force then acts for 4 second on the object and gives it a speed of 2 m/sec in opposite direction. The acceleration produced in it, is 

(1) 3 m/sec²

(2) –3 m/sec²

(3) 0.3 m/sec²

(4) –0.3 m/sec²

A machine gun is mounted on a 2000 kg car on a horizontal frictionless surface. At some instant the gun fires bullets of mass 10 gm with a velocity of 500 m/sec with respect to the car. The number of bullets fired per second is ten. The average thrust on the system is 

(1) 550 N

(2) 50 N

(3) 250 N

(4) 250 dyne

A cricket ball of mass 250 g collides with a bat with velocity 10 m/s and returns with the same velocity within 0.01 second. The force acted on bat is 

(1) 25 N

(2) 50 N

(3) 250 N

(4) 500 N

If rope of lift breaks suddenly, the tension exerted by the surface of lift (a = acceleration of lift) 

(1) mg

(2) m(g + a)

(3) m(g – a)

(4) 0

A plumb line is suspended from a ceiling of a car moving with horizontal acceleration of a. What will be the angle of inclination with vertical 

(1) tan^–1(a/g)

(2) tan^–1(g/a)

(3) cos^–1(a/g)

(4) cos^–1(g/a)

The linear momentum p of a body moving in one dimension varies with time according to the equation p = a + bt² where a and b are positive constants. The net force acting on the body is 

(1) A constant

(2) Proportional to t²

(3) Inversely proportional to t

(4) Proportional to t

A block \(A\) of mass \(7\) kg is placed on a frictionless table. A thread tied to it passes over a frictionless pulley and carries a body \(B\) of mass \(3\) kg at the other end. The acceleration of the system will be: (given \(g=10~\text{m/s}^2)\)

A body of weight 2kg is suspended as shown in the figure. The tension T₁ in the horizontal string (in kg wt) is 

(1) $2/\sqrt{3}$

(2) $\sqrt{3}/2$

(3) $2\sqrt{3}$

(4) 2

Two masses m₁ = 5 kg and m₂ = 4.8 kg tied to a string are hanging over a light frictionless pulley. What is the acceleration of the masses when they are free to move (g = 9.8 m/s²) 

(1) 0.2 m/s²

(2) 9.8 m/s²

(3) 5 m/s²

(4) 4.8 m/s²