Work, Energy And Power CBSE Questions & Answers

Two billiard balls each with a mass of 150g collide head-on in an elastic collision. Ball 1 was travelling at a speed of 2 m \({{\rm{s}}^ - }{\rm{1}}\) and ball 2 at a speed of 1.5 m \({{\rm{s}}^ - }{\rm{1}}\). After the collision, ball 1 travels away from ball 2 at a velocity of 1.5 m \({{\rm{s}}^{ - {\rm{1}}}}\) .What is the velocity of ball 2?

Consider the collision of two cars. Car 1 is at rest and Car 2 is moving at a speed of 2 m \({{\text{s}}^{{\text{ - 1}}}}\) in the negative x-direction. Both cars each have a mass of 500 kg. The cars collide inelastically and stick together. What is the resulting velocity of the resulting mass of metal?

A body of mass 0.5 kg travels in a straight line with velocity v =a \({{\rm{x}}^{{\rm{3}}/{\rm{2}}}}\) where a = 5 \({{\rm{m}}^{ - {\rm{1}}/{\rm{2}}}}{{\rm{s}}^{ - {\rm{1}}}}\) . What is the work done by the net force during its displacement from x = 0 to x = 2 m?

A person trying to lose weight (dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5 m each time. Assume that the potential energy lost each time she lowers the mass is dissipated. How much work does she do against the gravitational force?

A person trying to lose weight (dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5 m each time. Assume that the potential energy lost each time she lowers the mass is dissipated. Fat supplies 3.8 \({\times }\) \({\rm{1}}{0^{\rm{7}}}\) J of energy per kilogram which is converted to mechanical energy with a 20\(\% \) efficiency rate. How much fat will the dieter use up?

The Sun converts an enormous amount of matter to energy. Each second, 4.19 \({\times }\) \({\rm{1}}{0^{\rm{9}}}\) kg—approximately the capacity of 400 average-sized cargo ships—is changed to energy. What is the power output of the Sun?

A block having a mass of 0.80 kg is given an initial velocity 1.2 m/s to the right and collides with a spring of negligible mass and force constant k =50 N/m. Assuming the surface to be frictionless, calculate the maximum compression of the spring after the collision.

The launching mechanism of a toy gun consists of a spring of unknown spring constant. When the spring is compressed 0.120 m, the gun, when fired vertically, is able to launch a 35.0-g projectile to a maximum height of 20.0 m above the position of the projectile before firing. Neglecting all resistive forces, determine the spring constant.

A 3.00-kg crate slides down a ramp. The ramp is 1.00 m in length and inclined at an angle of 30.0\(^\circ \) . The crate starts from rest at the top, experiences a constant frictional force of magnitude 5.00 N, and continues to move a short distance on the flat floor after it leaves the ramp. Use energy methods to determine the speed of the crate at the bottom of the ramp.

A bullet of mass 0.012 kg and horizontal speed 70 m \({\rm{s}}{-^{\rm{1}}}\) strikes a block of wood of mass 0.4 kg and instantly comes to rest with respect to the block. The block is suspended from the ceiling by means of thin wires. Calculate the height to which the block rises. Also, estimate the amount of heat produced in the block.

A 1 kg block situated on a rough incline is connected to a spring of spring constant 100 N \({{\rm{m}}^{ - {\rm{1}}}}\) as shown in Figure. The block is released from rest with the spring in the unstretched position. The block moves 10 cm down the incline before coming to rest. Find the coefficient of friction between the block and the incline. Assume that the spring has a negligible mass and the pulley is frictionless.

A bolt of mass 0.3 kg falls from the ceiling of an elevator moving down with an uniform speed of 7 m/s. It hits the floor of the elevator (length of the elevator = 3 m) and does not rebound. What is the heat produced by the impact?

A trolley of mass 200 kg moves with a uniform speed of 36 km/h on a frictionless track. A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a speed of 4 m \({{\rm{s}}^{ - {\rm{1}}}}\) relative to the trolley in a direction opposite to the its motion, and jumps out of the trolley. What is the final speed of the trolley?

A trolley of mass 200 kg moves with a uniform speed of 36 km/h on a frictionless track. A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a speed of 4 m \({{\rm{s}}^{ - {\rm{1}}}}\) relative to the trolley in a direction opposite to the its motion, and jumps out of the trolley. How much has the trolley moved from the time the child begins to run?

A 50.0-kg marathon runner runs up the stairs to the top of a 443-m-tall Tower. To lift herself to the top in 15.0 minutes, what must be her average power output?