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Potential energy of an air bubble decreases because work is done by upthrust on the bubble

It is the total linear momentum.

Inelastic collision. 

When applied force is zero, friction is zero. As the applied force is increased, friction also increases and becomes equal to the applied force. It happens so, till the body does not start moving. For this reason, friction is called a self-adjusting force.

Friction is a self adjusting force as its value varies from zero to the maximum value to limiting friction. 

The magnitude of static friction depends on the magnitude of the applied force. As the applied force increases the magnitude of the static friction also increases. Thus static frictional force is a selfadjusting force.

The force of static friction varies in accordance with applied force. Hence, it is called as self adjusting force.

It is given that

Length of the godown = 40m

Breadth of the godown = 25m

Height of the godown = 15m

We know that

Volume of godown = l × b × h

By substituting the values

Volume of godown = 40 × 25 × 15

On further calculation

Volume of godown = 15000 m³

It is given that

Length of wooden crate = 1.5m

Breadth of wooden crate = 1.25m

Height of wooden crate = 0.5m

We know that

Volume of each wooden crate = l × b × h

By substituting the values

Volume of each wooden crate = 1.5 × 1.25 × 0.5

On further calculation

Volume of each wooden crate = 0.9375 m³

So we get

Number of wooden crates that can be stored in godown = Volume of godown/ Volume of each wooden crate

By substituting the values

Number of wooden crates that can be stored in godown = 15000/ 0.9375

So we get

Number of wooden crates that can be stored in godown = 16000

Therefore, the number of wooden crates that can be stored in the godown are 16000.

(b) Zero Joule

(a) The string becomes slack when the particle reaches its highest point. 
(d) The particle again passes through the initial position

Explanation: 

Since the particle is just able to complete the circle, at the highest point only its weight keeps it in circular path and tension in the string will be zero, Answer (a). 

(b) is not true because as given the particle completes a circle. At the highest point, it must have horizontal velocity =√(gl). 

(c) is not true because initial K.E. should be equal to ½mv² =mgl+½mgl. 

(d)Since no further work is done on the particle by an external force, the total mechanical energy of the system remains constant and the particle passes the initial position with same initial velocity.

(a) the force is always perpendicular to its velocity

(c) the object is stationary but the point of application of the force moves on the object
(d) the object moves in such a way that the point of application of the force remains fixed.

Explanation: 

Since there is no displacement along the force when it is perpendicular to the velocity of an object, so no work is done. Answer (a). (b) is not true because the acceleration will always be in the direction of force according to Newton's Second Law of Motion. 

No work is done if there is no displacement of the object in the direction of the force. Answer (c). 

Again there is no displacement along the force, no work done. Answer (d).

(a) The string becomes slack when the particle reaches its highest point. 
(d) The particle again passes through the initial position

Explanation: 

Since the particle is just able to complete the circle, at the highest point only its weight keeps it in circular path and tension in the string will be zero, Answer (a). 

(b) is not true because as given the particle completes a circle. At the highest point, it must have horizontal velocity =√(gl). 

(c) is not true because initial K.E. should be equal to ½mv² =mgl+½mgl. 

(d)Since no further work is done on the particle by an external force, the total mechanical energy of the system remains constant and the particle passes the initial position with same initial velocity.

(b) The resultant force on the particle must be at an angle less than 90° all the time. 

(d) The magnitude of its linear momentum is increasing continuously.

Explanation: 

Since K.E. of the particle continuously increases, means its velocity continuously increases i.e. it is accelerated. It can only happen if there is a positive component of the resultant force (F.cosθ) along the velocity. For it to happen the resultant force on the particle must be at an angle less than 90° all the time. Hence option (b). 

(a) is not true because it is only a special case of the condition in (b) when the angle θ=0° and it need not be a necessary condition. 

(c) is not true because the direction of the velocity is not given. 

(d) is true because the magnitude of v increases continuously hence the magnitude of linear momentum mv also increases continuously.

(b) The resultant force on the particle must be at an angle less than 90° all the time. 

(d) The magnitude of its linear momentum is increasing continuously.

Explanation: 

Since K.E. of the particle continuously increases, means its velocity continuously increases i.e. it is accelerated. It can only happen if there is a positive component of the resultant force (F.cosθ) along the velocity. For it to happen the resultant force on the particle must be at an angle less than 90° all the time. Hence option (b). 

(a) is not true because it is only a special case of the condition in (b) when the angle θ=0° and it need not be a necessary condition. 

(c) is not true because the direction of the velocity is not given. 

(d) is true because the magnitude of v increases continuously hence the magnitude of linear momentum mv also increases continuously.

Apparent weight is the weight of the body acquired due to the action of gravity and other external forces acting on the body.

i) Name of the given triangle is ΔPQR.

ii) The sides of ΔPQR are \(\overline{PQ},\overline{QR}\) and \(\overline{PR}\).

The angles of ΔPQR are ∠P, ∠Q and ∠R.

The vertices of ΔPQR are P, Q and R.

i) Cone 

ii) Cube 

iii) Sphere

iv) Cylinder

• wound
• regard
• design
• belief
• event

Nagendra was an orphan and had no job. He was clever and he had learned many things by observing his father. He decided to open a shop and sell wisdom.

Babu, a merchants son, was a stupid boy. He heard the wisdom seller and did not know what was really being sold. He thought wisdom was some kind of a vegetable or a thing he could hold in his hand.

Babu put down a nickel and asked Nagendra to give him a nickel’s worth of wisdom. Nagendra sold the wisdom, “It is not wise to stand and watch two people fighting”, for a nickel.

Correct option is (a) nerves

Babu’s father was angry’ because he had paid a nickel for a worthless piece of wisdom. He scolded his son for wasting money on a useless thing.

Correct option is (a) Oxygen

Nagendra made him sign a document which said that his son would not make use of the wisdom. When Gupta and Babu came again for his advice, he made Gupta pay a thousand rupees.

Babu followed the advice given by Nagendra. He pretended to be mad. When the king and the minister asked him questions, he just babbled incoherently. The king lost his patience and drove him out. Babu was happy because the trick was a success.

Babu stood and watched the quarrel between the two maids. Each of them wanted him to be her witness. The two queens threatened to get his head chopped off if he did not support them. So, Babu and his father went to Nagendra to buy wisdom. As advised by Nagendra, Babu pretended to be mad and escaped the king’s anger.’ Gupta did not want his son to act as a mad fellow always. For the second time they went to Nagendra to save themselves from the king’s wrath if he found out that Babu was not insane.

The two maids went to the same shop and both of them wanted to buy the same pumpkin. There was only one pumpkin. So, they started quarrelling.

The minister and one of the queens conspired to kill the king. The king followed the advice of Nagendra. He was able to find out the treachery of the minister and the queen. He sentenced them to death and made Nagendra his minister.

Correct option is (b) circulation

D) to pretend to be insane

B) each of the maids threatened to have his head chopped off if he did not support them

D) his wisdom had saved the king’s life

Correct option is (b) blood

(c) Simple and Cheap.

(b) This is India.

Correct Answer is: (d) Laziasm.

Correct Answer is: (a) 10’ to 12’

According to this law, "at constant temperature, the pressure of a fixed amount of gas is inversely proportional to its volume" P \(\propto\)\(\frac{1}{V}\)

(i) A group of organs that carry out similar functions in the body is called a system.

(ii) The process of keeping the blood flowing through all parts of the body is called blood circulation.

(iii) The process of converting food to simpler substances which can get mixed into blood easily is called digestion.

(iv) The process of entering of oxygen into the blood, so that it can be used to burn the food and release energy is called respiration.

All gases obey Charle's law at very low pressure and high temperature.

Correct Answer is: (a) Wealth.

At low pressures, volume V is very large and hence the correction term b (volume correction term) can be neglected in comparison to very large value of V. Thus, the van der Waals equation for 1 mole of a real gas.

\(\big(p+\frac{a}{V^2}\big)(V-b)\)RT may be written as

\(\big(p+\frac{a}{V^2}\big)(V)\) = RT

Or PV + \(\frac{a}{V}\) = RT

PV = RT - \(\frac{a}{V}\)

For large V (at very low pressure),\(\frac{a}{V}\) is very small and can be ignored.

\(\therefore\) PV becomes RT at very low pressure. That is why at very low pressure, real gases obey ideal gas equation.

Work function of a metal is the minimum energy required to knock out an electron (from the conduction band). Since electrons are present in a continuous band of levels, different electrons require different amounts of energy to get out of the atom. For this reason electrons knocked off by a monochromatic radiation posses different energies.

In part A, ratio of volume of hydrogen gas to that of nitrogen is nearly equal to 3 (actually in each of the three cases, the ratio is 2.94, 3.01 and 2.97. respectively). It indicates that the three molecules of hydrogen combine with one molecule of nitrogen to form one molecule of ammonia gas.

In part B, the ratio of the volume of hydrogen to that of oxygen is about 2 (actually in three cases, the ratio is 1.97, 2.00, 1.8 respectively. It indicates that two molecules of hydrogen combine with one molecule of oxygen to form one molecule of water.

From above, we find that the two gases combine chemically to yield another gas at the same temperature and pressure and the volumes of these gases bear simple ratio of small integers. This is the Gay Lussac's law. We can also understand the law on the basis of atomic picture and Avogadro's hypothesis.

Correct option is D. All these three

Naturally, the aunt thought of the story as improper. She thought that the bachelor’s story had undermined the effect of years of careful teaching. Though the aunt had her own reasons to think so, she should have also realized that if stories turn out to be merely preaching material, they fail to convince the children.

The Prince of the country came to know about Bertha from everybody who talked about her goodness.

The aunt’s story was built on the cliched idea that the good get rewarded. The little girl was saved from a mad bull by a number of rescuers who admired her moral character.

When Cyril saw some sheep in the field he wanted to know why the sheep were being driven from one field to another. When he was given the lame answer that the grass in the other field might be better, he wanted to know why it was better.