A body of mass M at rest explodes into three pieces, two of which of mass M/4 each are thrown off in perpendicular directions with velocities of 3 m/s and 4 m/s respectively. The third piece will be thrown off with a velocity of 

(1) 1.5 m/s

(2) 2.0 m/s

(3) 2.5 m/s

(4) 3.0 m/s

Which of the following graph depicts spring constant k versus length l of the spring correctly

(1)
(2)
(3)
(4)

Work done by a frictional force is

(1) Negative

(2) Positive

(3) Zero

(4) All of the above

A block of mass 50 kg slides over a horizontal distance of 1 m. If the coefficient of friction between their surfaces is 0.2, then work done against friction is 

(1) 98 J

(2) 72J

(3) 56 J

(4) 34 J

A body of mass m is moving in a circle of radius r with a constant speed v. The force on the body is $\frac{m{v}^2}{r}$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle

(1) $\frac{m{v}^2}{\pi r^2}$

(2) Zero

(3) $\frac{m{v}^2}{r^2}$

(4) $\frac{\pi r^2}{m{v}^2}$

A man pushes a wall and fails to displace it. He does:
1. negative work
2. positive but not maximum work
3. no work at all
4. maximum work

A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joules, the angle which the force makes with the direction of motion of the body is

(1) 0°

(2) 30°

(3) 60°

(4) 90°

A force acts on a 30 gm particle in such a way that the position of the particle as a function of time is given by $x=3t-4t^2+t^3$, where x is in metres and t is in seconds. The work done during the first 4 seconds is 

(1) 5.28 J

(2) 450 mJ

(3) 490 mJ

(4) 530 mJ

The minimum work done in pulling up a block of wood weighing \(2\) kN for a length of \(10\) m on a smooth plane inclined at an angle of \(15^\circ\) with the horizontal is (given: \(\mathrm{sin}15^\circ=0.2588)\):
1. \(4.36\) kJ
2. \(5.17\) kJ
3. \(8.91\) kJ
4. \(9.82\) kJ

A body of mass 6kg is under a force which causes displacement in it given by $S=\frac{t^2}{4}$ metres where t is time. The work done by the force in 2 seconds is-

(1) 12 J

(2) 9 J

(3) 6 J

(4) 3 J