Work Power And Energy Practice Questions

A cricket ball of mass $0.15 \ {kg}$ is thrownvertically up by a bowling machine so that itrises to a maximum height of $20 \ {m}$ after leaving the machine. If the part pushing the ball applies a constant force $\ {F}$ on the ball and moveshorizontally a distance of $0.2 \ {m}$ whilelaunching the ball, the value of $\ {F}($ in $\ {N})$ is $({g}=10 {ms}^{-2}\ )$ _______.

A small block starts slipping down from a point $\ {B}$ on an inclined plane $\ {AB},$ which is making an angle $\theta$ with the horizontal section $\ {BC}$ is smooth and the remaining section CA is rough with a coefficient of friction $\mu .$ It is found that the block comes to rest as it reaches the bottom (point A) of the inclined plane. If $\ {BC}=2 \ {AC}$ the coefficient of friction is given by $\mu=\ {k} \tan \theta$ ). The value of $\ {k}$ is _______.

A particle moves in one dimension from rest under the influence of a force that varies with the distance travelled by the particle as shown in the figure. The kinetic energy of the particle after it has travelled 3 m is:

A block of mass m, lying on a smoothhorizontal surface, is attached to a spring (ofnegligible mass) of spring constant k. The otherend of the spring is fixed, as shown in thefigure. The block is initally at rest in itsequilibrium position. If now the block is pulledwith a constant force F, the maximum speed ofthe block is : [9-Jan-2019 Shift 1]

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 particle which is experiencing a force, given by $\vec{F}$ = $3\hat{i}$ - 12 $\hat{j}$ , undergoes a displacement of $\vec{d}$ = $4\vec{i}$ . If the particle had a kinetic energy of 3 J at the beginning of the displacement, what is its kinetic energy at the end of the displacement?

A block of mass m is kept on a platform which starts from rest with constant acceleration g/2 upward, as shown in fig. Work done bv normal reaction on block in time t is :

A uniform cable of mass 'M' and length 'L' is placed on a horizontal surface such that its $(1 /n)^{th}$ part is hanging below the edge of the surface. To lift the hanging part of the cable upto the surface, the work done should be:

Two particles of the same mass m are moving in circular orbits because of force,given by $F(r)={-16}/r-r^3$ The first particle is at a distance $r=1$, and the second, at $r=4$. The best estimate for the ratio of kinetic energies of the first and the second particle is closest to :[Main 16 April 2018 S1]

A body of mass m starts moving from rest along x-axis so that its velocity varies as $υ=a\text{sqrts}$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 :[Main 16 April 2018 S1]

A particle is moving in a circular path of radius a under the action of an attractive potential $U=-k/{2r^2}$. Its total energy is :[Main 8 April 2018]

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 $v_0=10ms^{-1}$. If, after 10 s, its energy is $1/8mv^2_0$, the value of k will be:-[Main 2017]

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 :[Main 2017]

An object is dropped from a height h from the ground. Everytime it hits the ground it loses 50% of its kinetic energy. The total distance covered as $t\to \infty$ is :[Main 8 April 2017]

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 μ.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 μ and the distance x(=QR), are, respectively close to[Main 2016]

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 motionis :[Main 10 Apr 2016]

A car of weight W is on an inclined road that rises by 100 m over a distance of 1 km and applies a constant frictional force $W/20$ on the car. While moving uphill on the road at a speed of $10 ms^{-1}$, the car needs power P. If it needs power $P/2$ while moving downhill at speed $υ$ then value of $υ$ is :[Main 9 Apr 2016]

A person trying to lose weight by burning fat 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 $3.8\times 10^7J$ of energy per kg which is converted to mechanical energy with a 20 % efficiency rate. Take $g= 9.8\;ms^{-2}$ :[Main 2016]