answer all the questions above I will reward u 100 points
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Anonymous:
hiii
r u in 9th
i am also i know answers of these all
all these question r from physics chapter work and energy
right
yes work and energy
inbox me plz
i know the answers of all
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Hey friend,
Here are some answers you were looking for:
1.
I) Suma is doing work. This is because Suma is moving herself in water of the swimming pool by applying force.
II) A donkey is not doing work against gravity. This is because it is carrying load at right angles to the force of gravity.
III) A wind-mill is doing work. This is because it is lifting up water from the well against the force of gravity.
IV) A green plant is not doing work during photosynthesis. This is because the force as well as the distance moved are zero.
V) The engine does work in pulling a train. This is because an engine applies force due to which the train moves.
VI) No work is done when food grains are dried in the sun. Thus is because no force is applied and no motion takes place.
VII) Work is done when sailboat moves. Thus is because wind is applying force which produces motion in the sailboat.
2. Since the initial and final points of the path of an object thrown at an angle to the ground lie on the same horizontal line, the displacement of the object is only in the horizontal direction. Since there is no net displacement of the object in the vertical direction. Therefore, no work is done by the force of gravity on the object.
3. A battery contains chemicals and supplies electrical energy. So, a battery converts chemical energy inti electrical energy. In an electric bulb, the electrical energy is first converted into heat energy. This heat energy causes the filament of bulb to become white-hot and produce light energy. So, the energy changes involved when a battery lights up a bulb are:
Chemical energy -- Electrical energy -- Heat energy -- Light energy
4. The work done by the force will be equal to the change in kinetic energy when the velo itu changes from 5 m/s to 2 m/s
(I) Mass= 20kg
Velocity=5 m/s
K.E.=1/2mv^2
=1/2 × 20 × 5^2
=10 × 25
=250 J
(II) Mass=20kg
Velocity=2 m/s
K.E.=1/2mv^2
=1/2 × 20 × 2^2
=10 × 4
=40 J
Work done by force= Change in kinetic energy
= 250 - 40
210 J
5. The work done on the object by the gravitational force is zero. This is because the motion of the object is in the horizontal direction whereas the gravitational force is at right angles (90°) to the direction of motion of object.
W = F cos 90° × s
=F × 0 × s
=0
6. When a freely falling object comes downwards, it's height above the ground decreases due to which it's potential energy decreases progressively. Now, as the freely falling object comes down, it's speed goes on increasing due to which it's kinetic energy also goes on increasing. At any point of time during the free fall, the sum of potential energy and kinetic energy of the falling object remains the same. So, there is no violation of the law of conservation of energy in this case.
Answer 7 to 11 is in image.
12. Yes, there can be displacement of an object in the absence of any force acting on it. We know that F= m × a. Now, when force is 0, then m × a = 0. Since mass cannot be zero, therefore when force F=0, then acceleration = 0. In such situation, either the object is at rest or it is in uniform motion in a straight line. There is a displacement of the object without any force acting on it.
HOPE MY ANSWER WOULD BE HELPFUL TO YOU!!!!!!!☺☺
Here are some answers you were looking for:
1.
I) Suma is doing work. This is because Suma is moving herself in water of the swimming pool by applying force.
II) A donkey is not doing work against gravity. This is because it is carrying load at right angles to the force of gravity.
III) A wind-mill is doing work. This is because it is lifting up water from the well against the force of gravity.
IV) A green plant is not doing work during photosynthesis. This is because the force as well as the distance moved are zero.
V) The engine does work in pulling a train. This is because an engine applies force due to which the train moves.
VI) No work is done when food grains are dried in the sun. Thus is because no force is applied and no motion takes place.
VII) Work is done when sailboat moves. Thus is because wind is applying force which produces motion in the sailboat.
2. Since the initial and final points of the path of an object thrown at an angle to the ground lie on the same horizontal line, the displacement of the object is only in the horizontal direction. Since there is no net displacement of the object in the vertical direction. Therefore, no work is done by the force of gravity on the object.
3. A battery contains chemicals and supplies electrical energy. So, a battery converts chemical energy inti electrical energy. In an electric bulb, the electrical energy is first converted into heat energy. This heat energy causes the filament of bulb to become white-hot and produce light energy. So, the energy changes involved when a battery lights up a bulb are:
Chemical energy -- Electrical energy -- Heat energy -- Light energy
4. The work done by the force will be equal to the change in kinetic energy when the velo itu changes from 5 m/s to 2 m/s
(I) Mass= 20kg
Velocity=5 m/s
K.E.=1/2mv^2
=1/2 × 20 × 5^2
=10 × 25
=250 J
(II) Mass=20kg
Velocity=2 m/s
K.E.=1/2mv^2
=1/2 × 20 × 2^2
=10 × 4
=40 J
Work done by force= Change in kinetic energy
= 250 - 40
210 J
5. The work done on the object by the gravitational force is zero. This is because the motion of the object is in the horizontal direction whereas the gravitational force is at right angles (90°) to the direction of motion of object.
W = F cos 90° × s
=F × 0 × s
=0
6. When a freely falling object comes downwards, it's height above the ground decreases due to which it's potential energy decreases progressively. Now, as the freely falling object comes down, it's speed goes on increasing due to which it's kinetic energy also goes on increasing. At any point of time during the free fall, the sum of potential energy and kinetic energy of the falling object remains the same. So, there is no violation of the law of conservation of energy in this case.
Answer 7 to 11 is in image.
12. Yes, there can be displacement of an object in the absence of any force acting on it. We know that F= m × a. Now, when force is 0, then m × a = 0. Since mass cannot be zero, therefore when force F=0, then acceleration = 0. In such situation, either the object is at rest or it is in uniform motion in a straight line. There is a displacement of the object without any force acting on it.
HOPE MY ANSWER WOULD BE HELPFUL TO YOU!!!!!!!☺☺
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