JEE Main Work Power & Energy Practice Questions With Solutions

A block of mass $1\mathrm{kg}$1 \textrm{ } kg is pushed up a surface inclined to horizontal at an angle of ${60}^{\circ }$60^{\circ} by a force of $10\mathrm{N}$10 \textrm{ } N parallel to the inclined surface as shown in figure. When the block is pushed up by $10\mathrm{m}$10 \textrm{ } m along inclined surface, the work done against frictional force is :

$[g=10\mathrm{m}/{\mathrm{s}}^2]$\left[\right. g = 10 \textrm{ } m / s^{2} \left]\right.

A particle is placed at the point $A$A of a frictionless track $ABC$A B C as shown in figure. It is gently pushed towards right. The speed of the particle when it reaches the point B is :

(Take $g=10\mathrm{m}/{\mathrm{s}}^2$g = 10 \textrm{ } m / s^{2}).

A bob of mass '$m$m' is suspended by a light string of length '$L$L'. It is imparted a minimum horizontal velocity at the lowest point $A$A such that it just completes half circle reaching the top most position B. The ratio of kinetic energies $\frac{(K.E{)}_A}{(K.E{)}_B}$\frac{\left(\right. K . E \left.\right)_{A}}{\left(\right. K . E \left.\right)_{B}} is :

A block of mass $100\mathrm{kg}$100 \textrm{ } kg slides over a distance of $10\mathrm{m}$10 \textrm{ } m on a horizontal surface. If the co-efficient of friction between the surfaces is 0.4, then the work done against friction $(\mathrm{in}J$\left(\right. in J) is :

The potential energy function (in $J$J ) of a particle in a region of space is given as $U=(2x^2+3y^3+2z)$U = \left(\right. 2 x^{2} + 3 y^{3} + 2 z \left.\right). Here $x,y$x , y and $z$z are in meter. The magnitude of $x$x-component of force (in $N$N ) acting on the particle at point $P(1,2,3)\mathrm{m}$P \left(\right. 1 , 2 , 3 \left.\right) m is :

A bullet is fired into a fixed target looses one third of its velocity after travelling $4\mathrm{cm}$4 \textrm{ } cm. It penetrates further $\mathrm{D}\times {10}^{-3}\mathrm{m}$D \times 10^{- 3} \textrm{ } m before coming to rest. The value of $\mathrm{D}$D is :

The ratio of powers of two motors is $\frac{3\sqrt{x}}{\sqrt{x}+1}$\frac{3 \sqrt{x}}{\sqrt{x} + 1}, that are capable of raising $300\mathrm{kg}$300 \textrm{ } kg water in 5 minutes and $50\mathrm{kg}$50 \textrm{ } kg water in 2 minutes respectively from a well of $100\mathrm{m}$100 \textrm{ } m deep. The value of $x$x will be

Two bodies are having kinetic energies in the ratio 16 : 9. If they have same linear momentum, the ratio of their masses respectively is :

Given below are two statements:

Statement I : A truck and a car moving with same kinetic energy are brought to rest by applying breaks which provide equal retarding forces. Both come to rest in equal distance.

Statement II : A car moving towards east takes a turn and moves towards north, the speed remains unchanged. The acceleration of the car is zero.

In the light of given statements, choose the most appropriate answer from the options given below

A bullet of mass $0.1\mathrm{kg}$0.1 \textrm{ } kg moving horizontally with speed $400{\mathrm{ms}}^{-1}$400 \left(\textrm{ } ms\right)^{- 1} hits a wooden block of mass $3.9\mathrm{kg}$3.9 \textrm{ } kg kept on a horizontal rough surface. The bullet gets embedded into the block and moves $20\mathrm{m}$20 \textrm{ } m before coming to rest. The coefficient of friction between the block and the surface is __________.

(Given $g=10\mathrm{m}/{\mathrm{s}}^2$g = 10 \textrm{ } m / s^{2} )