Select Board & Class
derive relationship between commercial unit of energy and si unit of energy
A body moving in a straight line at 72kmph undergoes an acceleration of 4m/s2. Find its speed after 2 seconds.
is ncert solutions for computer science avalable
calculate the work required to be done to stop a car of 1500kg moving at a velocity of 60km/h?
1 watt of power:
if a force F is applied on a body and it moves with velocity v , the power will be :
what is the relation between KW h and joules
What is the formula of sulphide ion,sulphate ion,sulphur ion ?
Force acting on a particle moving in a straight line varies with the velocity of the particle as F=k/v,where K is a constant.The work done by this force in time t is:
Q- Give one example of:-
(a) Certain force acting on a 20kg mass changes its velocity from 5m /s to 2 m/s . calculate the work done by the force .
(b) State two possible condition under which the work done would be zero.
(c) if the kinetic energy of the body is increased by 300% then determine the percentage increase in the momentum.
If an electrical appliance is rated 1000 W and is used for 2 hours . Calculate the work done in 2 hours .
the power of motor pump is 2kW. how much water per minute the pump can raise to a height of 10m? (given g = 10m/s)
In an oscillating pendulum, at what positions the potential and kinetic energy are maximum?
suggest me a working science model for class 9th
The kinetic energy of an object of mass , m moving with a velocity of 5m/s is 25J.what will be its kinetic energy when its velocity is doubled ?what will be its kinetic energy when its velocity is incrased three times
a body of mass 2 kg is thrown vertically upwards with the initial velocity of 20 m s-1. what will be its potential energy at the end of 2 seconds.(g=10m s-2)
What is the derivation of Kinetic energy and Potential energy
What is the work done to increase the velocity of a car from 30km/h to 60km/h if the mass of the car is 1500kg?
the kE acquired by a mass m in travelling a certain distance s ,starting from rest ,under the action of a constant force is directly proportional to:
d)none of these
A bag of wheat weighs 50 kg, find the height to which it should be raised so that potential energy is 5000 J(g = 10m/s2)?
Q1. The volume of 50g of a substance is 20cm3 . If the denstiy of water is 1 g cm3, will the substance float or sink in water ? justify your answer ?
Q2. Show that the energy of a vibrating pendulum is conserved ?
Q3. A ball is dropped from a heigh of 10m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back ?
define 1 watt of power?
define work , its formula with SI unit ?
define power. Give the SI unit of power
Which of the following statements about the work done by a force is incorrect?
Work is done by a force only if a body moves towards the direction of the applied force.
Work done by a body is equal to the amount of energy gained or spent by the body.
Work done by a force can be zero even if the body moves to a certain distance.
Work done by a force can be positive as well as negative.
Work done by a force is defined as the product of the force on a body and the displacement of the body along the line of action of the force. Therefore, it is not necessary that the body always moves towards the direction of the applied force. Even if a body moves opposite to the direction of the applied force, work is done by the applied force. This is because the displacement of the body is along the line of action of the applied force. In this case, the work done by the force is considered negative.
The correct answer is A.
Dear Experts, I can't understand this. How can it be not necessary that an objectalways moves towards the direction of the applied force?
If the above is correct, then please coin an example.
Derive an expression for the gravitational potential energy of an object of mass 'm' at a height 'h' above the earth's surface.
A stone projected vertically upward with a velocity 'u' reaches a maximum height 'h'. Find the ratio of kinetic energy and potential energy of the stone, when it is at height 3h/4 from the ground..?
1. Can a body have energy without momentum ????
2. Can a body have momentum without energy ?????
plzz ans. with explanation ???
Identify and state the type of transformation of energy in the following cases:
1. When coal is burnt.
2. When a dry cell discharges.
3. In a thermal power plant.
Can any object have momentum even if its mechanical energy is 0? explain.
Take the readings of the electric meter each day at 6.30 am and 6.30 pm. How many ‘units’ are consumed during day time?How many ‘units’ are used during night? • Do this activity for about a week. • Tabulate your observations. • Draw inferences from the data. • Compare your observations with the details given in the monthly electricity
What is the work done by a satellite moving around the earth ?Justify your answer.
An object of mass of 20 kg is dropped from a height of 4 m. Fill in the blanks in the following table by computing the potential energy and kinetic energy in each case.
height at which object is located: 4 m, 3 m, 2m, 1m, just above the ground
(for simplifying the calculations, take the value of g as 10 m s-2)
A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy
1)a boy weighing 350 N runs up a hight of 30 steps . each 0.2m high .calculate the work done
2)it takes 20s for A to climb up a stair while B does the same in 15 s. Compare the work done and power developed by aand b.
3) A WEIGHT LIFTER LIFTED A WEIGHT OF 200 kgf to a height of 2.5 m in 5 s. Calculate 1)the work done 2) the power developed by him (take g = 10ms2)
4) a car of mass 2000 kg is lifted up a distance of 30m by a crane in 60 s. A second crane does the same job in 120s . do the cranes consume the same or different amounts of fuel.
5) how much work can a 2 horse power motor do in one hour
6)a man does 800 j of work in lifting a 40 kg bucket from a well .calculate the depth of the well. (g= 10m/s2)
7) a Sherpa of mass 80 kg is instructed to carry a package of 20 kg from t he base camp to summit of a mountain 1200 m high . 1) how much work the Sherpa has to do againdt the gravity 2) also find the change in the potential energy at the base of the mountain is taken as zero.(g=10m/s2)
8)in how much time can a water pump of 500w ,lift 1000kg of water to an overhead tank at a height of 7m.
If the speed of a body is halved ,what will be the change in its kinetic energy??????????
Derive the relation between momentum and kinetic energy ??????
why iron nail sinks and cork float on water?
name the form of energy associated in each case:
flying bird, man climbing stairs,compressed watch spring,fast moving objects
I am confused as to how to find K.E. in the Activity 11.15 at Page 155 of Work and Energy chapter because we don't know the velocity in those cases. Finding P.E. is easy there. Can anybody help???
an electric heater is rated 1500w. how much energy does it use in 10 hrs.express your answer kwt and joules.
wat is the relationship between JOULE (J) and ERG ??????
experts answer ??:DD
1. A block of 20 kg is pulled up by applying a force acting parallel to the slope. If the slope makes an angle of 30 degree with the horizontal, calculate the work done in pulling the load by a distance of 3m. What is the increase in potential energy of the block. (g = 10 newton per kg)
2. The speed of a bicycle decreases from 18 to 9 kmph. If the total mass of cyclist including the cycle is 70 kg, calculate the work done in overcoming the friction offered by the brakes & the road. Does the kinetic energy of the system also reduce to half its initial value?
derive an expression for kinetic energy of a body ?
When do we say that work is done?
A sling which is kept compressed by tying its ends together is allowed to be dissolved in acid.what happens to the potential energy of the spring?
A boy of mass 55 kg runs up a flight of 40 stairs each measuring 0.15m. Calculate the work done by the boy?
can you plz give me the examples of kinetic energy?????????????
I have some doubts in the following questions:
Chapter : WORK , ENERGY AND POWER
1. A body of mass 2 kg is dropped from the top of a tower of height 100 m. If
the acceleration due to gravity is 10 m/s2
calculate the K.E at the end of 5
2. A body of mass 2 kg is thrown vertically upwards with an initial velocity of
. What will be its P.E at the end of 2 s . ( Take g as 10 m/s2
3. A body is thrown vertically upwards .its velocity keeps decreasing. What
happens to its K.E as velocity becomes zero. Find the energy present in an
object of mass 10 kg when it is at a height of 6m above the ground. Given
g= 9.8 m/s2
4. A porter lifts a luggage of 15 kg from the ground and puts it on her head 2m
above the ground. Calculate the work done by her on the luggage. (Take g=
5. A rocket of mass 3x 10 6
kg mass takes off from a launching pad and attains
a velocity of 1 km/h at an attitude of 25 km. Calculate the P.E and K.E .
6. An object of mass 40 kg is raised to a height of 5m above the ground. What
is the P.E. if the object is allowed to fall, find the K.E when it is half way
down. Take g as 10 m/s2
7. A boy of mass 40 kg runs up a flight of 15 steps, each 15 cm high in 10 s.
Find the work done and the power developed by him. (Take g=10m/s2
8. Two bodies of equal masses move with uniform velocities of v and 3v
respectively. Find the ratio of their kinetic energies.
9. What is the work done to increase the velocity of a car from 30 km/h to
60 km/h. Let the mass of the car be 1500 kg.
10. On a level road, a scooterist applies brakes to slow down from a speed of
36 km/h to 18 km/h. Find the work done by the brakes, assuming the mass
of the empty scooter to be 86 kg and that of the person and petrol equal to
11. How much time will a pump of 1 kW power take to lift 500kg of water to
height of 40 m ? (Take g=10m/s2
12. A horse exerts a pull on the cart of 300 N so that the horse-cart system
moves with a uniform speed of 18 km/h on a level ground. Calculate the
power developed by the horse in watt and also find its equivalent in
Water is falling on the Blades of a turbine at the rate of 6 * 103 kg per minure .
The height of the fall is 10 m . Claculate the power given to the turbine. Take g = 10 m/s2
what is the proof for w = F S cos theta
think of some situations in your daily life in daily work, list them. is work done in each situation, if work is done. which is the force acting on the object . what is the object on which the work is done. what happens to the object on which work is done.
a truck and a car moving with same kinetic energy are stopped by applying same retarding force by means of brakes. which stops at a smaller distance?
define density?Give its SIunit.
a man drops 10kg rock from the top of a 5m ladder. wht is its speed just before it hits the ground? wht is its kinetic energy wen it reaches da ground.
please answer fast.tommorow i have an exam
examples of kinetic enery and potential energy its urgent
Water stored in a dam possesses
(a) no energy (b) electrical energy (c) kinetic energy (d) potential energy
how would you separate dyes in black-black ink using chromatography
Derive an expression for the kinetic energy of an object of mass 'm' moving horizontally with a uniform velocity 'v'
two bodies of masses (m1) and (m2) have equal kinetic energy. what shall be the ratio of their momentum
A men weighing 70kg carries a weight of 10kg on the top of tower 100m high. Calculate the work done by the man (g=10m/s2).
prove that the energy remains constant in case of a freely falling body....
when is the work done by a force said to be negative? give one situation in which one of the forces acting on the object is doing positive and other is doing negative work.
An object of mass 40kg is raised to a height of 5m above the ground.What is its PE?If the object is allowed to fall,find its KE when it is half way downAn object of mass 40 kg is raised to a height of 5m above the ground.What is its PE?If the object is allowed to fall,find its KE when it is half way down
A 1000 kg elevator rises from rest in the basement to the fourth floor,a distance of 20m.As it passes the fourth floor its speed is 4m/s. There is a constant frictional force of 500N. The work done by the lifting mechanism is:
define average power
name the physical quantity defined by rate of doing work. define its S.I unit
Explain the transformation of energy in hydroelectric power plant?
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