List of top Physics Questions on work, energy and power asked in JEE Main

A force acts on a $2\, kg$ object so that its position is given as a function of time as $x = 3t^2 + 5$. What is the work done by this force in first $5$ seconds ?

A man (mass = $50\, kg$) and his son (mass = $20\, kg$) are standing on a frictionless surface facing each other. The man pushes his son so that he starts moving at a speed of $0.70\, ms^{-1}$ with respect to the man. The speed of the man with respect to the surface is :

A block of mass $m$, lying on a smooth horizontal surface, is attached to a spring (of negligible mass) of spring constant $k$. The other end of the spring is fixed, as shown in the figure. The block is initally at rest in its equilibrium position. If now the block is pulled with a constant force $F$, the maximum speed of the block is :

A proton of mass m collides elastically with a particle of unknown mass at rest. After the collision, the proton and the unknown particle are seen moving at an angle of $90^{\circ}$ with respect to each other. The mass of unknown particle is :

A thin rod $MN$, free to rotate in the vertical plane about the fixed end $N$, is held horizontal. When the end $M$ is released the speed of this end, when the rod makes an angle $\alpha$ with the horizontal, will be proportional to : (see figure)

A body of mass m starts moving from rest along x-axis so that its velocity varies as $v = a \, \sqrt{s}$ where a is a constant and s is the distance covered by the body. The total work done by all the forces acting on the body in the first t seconds after the start of the motion is :

A particle is moving in a circular path of radius a under the action of an attractive potential $U = - \frac{k}{2r^2}$. Its total energy is -

In a collinear collision, a particle with an initial speed $v_0$ strikes a stationary particle of the same mass. If the final total kinetic energy is $50 \%$ grater than the original kinetic energy, the magnitude of the relative velocity between the two particles, after collision, is -

The mass of a hydrogen molecule is $3.32 \times 10^{-27} \, kg$. If $10^{23}$ hydrogen molecules strike, per second,a fixed wall of area $ 2 \, cm^2$ at an angle of $45^{\circ} $ to the normal, and rebound elastically with a speed of $10^3 \, m/s$ , then the pressure on the wall is nearly :

A body of mass $m=10^{-2} \, kg$ is moving in a medium and experiences a frictional force $F=-kv^2$. Its initial speed is $v_0=10 \, ms^{-1}$. If, after $10\,s$, its energy is $\frac{1}{8} mv_0{^{2}}$, the value of $k$ will be :

A time dependent force $F = 6t$ acts on a particle of mass $1\,kg$. If the particle starts from rest, the work done by the force during the first $1\,sec$. will be :

Two particles $A$ and $B$ of equal mass $M$ are moving with the same speed $v$ as shown in the figure. They collide completely inelastically and move as a single particle $C$. The angle $\theta$ that the path of $C$ makes with the $X-axis$ is given by :

A person trying to lose weight by burning at lifts a mass of $10\, kg$ upto a height of $1\, m$ $1000$ times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up ? Fat supplies $3.8 \times 10^7 \, J$ of energy per kg which is converted to mechanical energy with a $20\%$ efficiency rate. Take $g = 9.8 \, ms^{-2}$ :

A point particle of mass $m$, moves along the uniformly rough track $PQR$ as shown in the figure. The coefficient of friction, between the particle and the rough track equals $\mu$. The particle is released, from rest, from the point $P$ and it comes to rest at a point $R$. The energies, lost by the ball, over the parts, $PQ$ and $QR$, of the track, are equal to each other, and no energy is lost when particle changes direction from $PQ$ to $QR$. The values of the coefficient of friction $\mu$ and the distance $x(=QR)$, are, respectively close to :

A particle of mass $M$ is moving in a circle of fixed radius $R$ in such a way that its centripetal acceleration at time $t$ is given by $n^2 \, R \, t^2$ where $n$ is a constant. The power delivered to the particle by the force acting on it, is :

Velocity-time graph for a body of mass $10\, kg$ is shown in figure. Work-done on the body in first two seconds of the motion is :

A spring of unstretched length \(\ell\) has a mass m with one end fixed to a rigid support. Assuming spring to be made of a uniform wire, the kinetic energy possessed by it if it's free end is pulled with uniform velocity \(\upsilon\) is :

A bullet looses $\left(\frac{1}{n}\right)^{th}$ of its velocity passing through one plank. The number of such planks that are required to stop the bullet can be :

When a rubber -band is stretched by a distance x, it exerts a restoring force of magnitude $ F = ax + bx^2$, where a and b are constants. The work done in stretching the unstretched rubber-band by $L$ is :

A projectile of mass $M$ is fired so that the horizontal range is $4\, km$. At the highest point the projectile explodes in two parts of masses $M/4$ and $3M/4$ respectively and the heavier part starts falling down vertically with zero initial speed. The horizontal range (distance from point of firing) of the lighter part is :

Find the amount of work done in rotating a dipole of dipole moment $3\times {10}^{-3}cm$ from its position of stable equilibrium to the position of unstable equilibrium, in a uniform electric field of intensity ${10}^4{NC}^{-1}$.

A block of mass m = 50 kg is lifted from ground to a height of 20 m in two different ways as shown in the figure. Find the ratio of work done by gravity in both the cases.

A heater of rating of 50 W – 200 V is connected with source voltage of 100 V. Power consumed by heater is