UNIT#02 WORK AND ENERGY Flashcards
A truck and a car move with equal velocity. On applying brakes, both will stop after a certain distance.
The car will cover less distance before stopping
(being lighter than a truck, the car has less kinetic energy)
What sort of energy does a flying bird possess?
➡Potential Energy
➡Kinetic Energy
When the velocity of an aeroplane is doubled, the momentum ____.
Is conserved
(as the momentum of air also increases)
A machine gun fires 60 bullets per minute, with a velocity of 700m/s. If each bullet has a mass of 50g, find the power developed by the gun
12250W
(P=W/t=K.E/t)
A bullet fired from a gun can pierce a target due to its
Kinetic Energy
Kinetic energy with any reference must be:
Positive
At what angle, work done will be maximum?
0°
Which one of the following is a greater work?
-1000J
Work done will be zero if the angle between Force and Displacement is;
270°
A force 2i + j has moved its point of application from (2,3) to (6,5). What is work done?
+10
(➡d=(6-2)i + (5-3)j
➡W=Fd)
At what angle the work done will be half of its maximum value:
60°
A man pushes a wall with 50N and it displaces it zero m, his work done is:
No work
If a mass of 5kg is lifted up to 5m height, what will be the work done against the gravitational field
245J
A person walks 2m with an acceleration of 5 m/s2, holding an object of mass 2kg. The net work done on the object is:
20J
A force of 3i+2j+4k N gives a displacement of 10jm. The work done is:
20J
A body travels displacement of 10m by force of 5N. If work done is 25J then the angle between F and d is:
60°
A person holds a bucket of wight 60N. He walks 7m along the horizontal path and climbs up a vertical distance of 5m. The work done by the gravity is:
300 N-m
Suppose the force and displacement of a particle in the direction of force are doubled. Work would be:
4 times
A person is holding a bucket by applying a force of 10N. He moves a horizontal distance of 5m and then climbs a vertical distance of 10m. Could you find the total work done by him?
100J
A gardener pushes a lawn roller through a distance of 20m. If he applies a force of 20kg weight in a direction inclined at 60° to the ground, find the work done by him
1960J
If velocity is double, then:
Momentum increases 2 times and K.E increases 4 times
What will be the ratio of an alpha particle and proton kinetic energies if their linear momentum is the same?
1:4
The bodies of one kg and four kg have the same kinetic energy. The ration in their momenta will be:
1:2
The velocity and momentum of a moving body are 10000 cm/s and 10000 g cm /s respectively. The K.E will be:
Four Times
The momentum and kinetic energy of a ball are numerically equal. The numerical velocity is;
2 m/s
The kinetic energy of a body moving at the speed of 10m/s is 30J. If its speed becomes 30m/s, its K.E will be:
270J
Car X is travelling at half the speed of ar Y. Car X has twice the mass of car Y. Which statement is correct?
Car X has half the kinetic energy of car Y
A ball of mass 2kg and another of mass 4kg are dropped together from a 60 feet tall building. After a gall of 30 feet each towards earth, their respective kinetic energies will be in the ratio of:
1:2
A bomb of mass of 30kg at rest explodes into two pieces of masses 18kg and 12kg. The velocity o 18kg mass is 6 m/s.The K.E of other masses is:
486J
The kinetic energy acquired by a body of mass m is travelling some distance s, starting from rest under the actions o a constant force, is directly proportional to;
m^0
(Does not depend upon mass)
When force and displacement are in the same direction, the kinetic energy of the body.
Increases
A truck and a car are moving with equal velocity. On applying brakes, both will stop after a certain distance, then?
The car will cover less distance before stopping
Potential energy per unit volume is given by:
ρgh
A body is falling from a height h. After it has fallen a height of h/2, it will possess
Hal Potential and Half Kinetic Energy
Energy stored in the spring of which is:
Elastic Potential Energy
Initially, four identical uniform blocks, each of mass m and thickness h, are spread on a table, work require to stack them on one another is;
6 mgh
(W= n(n-1)/2 mgh)
A stone is thrown up from the surface of earth when it reaches maximum height. Its total energy is equal to;
mgh
Energy consumed by a 60-watt bulb in 2 minutes is equal to;
7.2 kilojoules
The consumption of energy by a 60-watt bulb in 2 seconds is:
120J
100 Joules work has been done by an agency in 10 seconds. What is the power of energy?
10 watt
A 500N force is applied to an object and it moves with a velocity of 10m/s.If the value of power is 2500watt.Then what will be the angle between force and displacement?
60°
(cos 60°=1/2)
The time taken by an engine of power 10kW to lift a mass of 200kg to the height of 40 m is:
8 sec
(P=mgh/t)
To travel at a constant speed, a car engine provides 24kW of useful power. The driving force on the car is 600N. At what seed does it travel?
40 m/s
(P=Fv)
A force of 1000 N is needed to lift the hook of a crane at a steady velocity The crane is then used to lift a load of mass 1000kg at a velocity of 0.50m/s.How much much of the power developed by the motor of the crane is used in lifting the hook and the load?
5.5 kW
The power output of a lamp is 6W. How much energy does the lamp give out in 2 minutes?
720 J
A man M1 of mass 80kg runs up a staircase in 15 sec. Another man M2 also of mass 80kg runs up the same staircase in 20 sec. The ratio o the power developed by them will be:
4/3
An engine pumps out 100kg of water through a height of 10 m in 5s. Given that the efficiency of the engine is 60%m what is the power of the efficiency?
3.3 kW
%age change in any quanitity= {(1±n)^k -1} x 100
An engine pumps up 40kg of water through a height of 10m in 5 sec. The water comes out vertically upwards with a velocity of 3m/s. What is the power of the engine in kilowatts?
1.2 kW
An elevator’s motor produces 3000 W power. The speed with which it can lift a 1000kg load is;
0.306 m/s
The power needed to lift a mass of 5000g to a height of 1m in 2 seconds is:
24.5 watt
An engine pulls a car of mass 1500kg on a level road at a constant speed of 5 m/s.If the frictional force is 500N, what power does the engine generates?
2.5 kW
Work done on a body equals the change in its ____ energy.
Total
If a certain force acts on an object and changes its kinetic energy from 65J to 130J. Then work done by the force will be:
651J
(According to Work-Energy Principle,
Work Done=Kinetic Energy
The amount of work required to stop a moving object is equal to;
The kinetic energy of the object
The work-energy principle is valid for:
All types of Energies
The mathematical form of work energy principle is:
Fd= 1/2 mvf^2 - 1/2 mvi^2
Unit of energy:
Joule
Work done will be maximum if the angle between the force F and displacement d is:
0°
A field in which the work is done in moving a body along a closed path is zero is called:
Conservative Field
When a force is parallel to the direction of motion of the body, then work done is:
Maximum
If a body with a mass of 2kg is raised vertically through 2m, then the work done will be:
39.2 J
The relation between horsepower and watt is:
1 hp = 746 watt
The slope of the work time graph is equal to:
Power
The consumption of energy by a 60-watt bulb in 2 sec is:
120J
A man lifts vertically a weight of 40kg through 1m in 10sec, while a child lifts vertically a weight of 10kg through a distance of 1m in 1s. What will be the correct inference?
Man does more work than the child
The area under the force-displacement graph represents:
Work Done
When can one say that work is done on the body:
When there is an increase in energy because of mechanical influence
The work done on an object does not depend upon the:
The initial velocity of the object
A machine does 2500J of work in 1min. What is the power developed by the machine?
42W
A moving car possesses:
Mechanical Energy
The interconversion of matter and energy is predicted by:
Einstein
A bus weighing 12kN has a speed of 20 m/s. Its kinetic energy is;
240 kJ
According to the law of conservation of energy:
➡Energy cant be destroyed
➡Energy can’t be created
➡Energy can be transformed from one form to the other
kWh is the unit of:
Energy
An object that has potential energy has this energy because of its:
Location
The power of an agent is:
➡The rate of generation of energy
➡The rate of transfer of energy
➡The rate of consumption of energy
Unit of energy:
➡Joule
➡Calorie
➡KiloJoule
Power delivered by the water pump on lifting:
P=mgh/t
2kg mass is uplifted by the machine through the height o 200m for 10 sec. Calculate the power delivered to the load.
400W
Light body A and heavy body B have equal K.E of translation. The:
B has larger momentum than A
The Energy required to accelerate a car from 10ms to 20 m/s compared with that required to accelerate is from 0 to 10 is:
Four times
The kinetic energy of a body is 1000J, its momentum decrease by 50% then the kinetic energy of that body becomes:
750J
Work done will be maximum. If the angle between the force F and displacement is:
0°
Which of the following have the same dimension:
➡Energy
➡Work
The slope of the work time graph is equal to:
Power
If the velocity is doubled then:
➡Momentum increases 2 times
➡K.E increases 4 times
What is the average power required to lift a mass of 100kg to a height of 50m in 50 seconds?
980
When one can say that work is done on the body:
When there is an increase in energy because of mechanical influence
In the case of negative work, the angle between the force and displacement is:
180°
