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Adi   from ,
Subject :Physics    Class : Class 8

Case study :A ball of mass 20 g is initially moving with a velocity of 50 m s–1 and acquires some linear momentum. If we apply a constant force F on the ball for 2.0 s, its velocity changes to 70 m s–1 and as a result linear momentum of the ball also changes. This change in linear momentum of the ball is brought about by a suitable magnitude of applied force F and the time during which this force is exerted. This led to second law of motion. Further the linear momentum of the ball will change in the direction of the applied force.
What is the rate of change of linear momentum?

A 1.4 N
B 2.0 N
C 0.2 N
D 1.0 N


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Ehan Gowrav   from Nps BSK, Bengaluru
Subject :Physics    Class : Class 6

Case Study : You have already learnt that if you know the distance between places, you can decide the mode of transport to reach our destination. Therefore, human beings not only realized the need but also devised methods for various measurements. In order to measure any particular quantity, you should know the unit of measurement and the number of units that particular quantity measures. In ancient times, people used handspan, cubit, arm length and footstep as different units of measurement of length and distance. Different standard units of measurement were created at different places.
For the sake of uniformity, scientists of all over the world have accepted a set of standard units of measurement. This standard system of unit is known as international system of units.
Identify the correct one.

A 15 kgs
B 15 Kg
C 15 kgs
D 15 kg


Both the B and D options are the same as well as the A and C options, if both are correct then shouldn't B also be correct

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Ansh Dhakate   from SNBP Chikhali, Pune
Subject :Physics    Class : Class 6

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Rishith chowdary   from Kennedy high global school , Hyderabad
Subject :Physics    Class : Class 7

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Sanchi Gajanan Patil   from Nagarjuna Public school , Nanded
Subject :Physics    Class : Class 8

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Yashraj Deshmukh   from Sahyadri English School, Loha, Nanded
Subject :Physics    Class : Class 7

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Daanish Nagpuria   from The HDFC School , Gurgaon
Subject :Physics    Class : Class 6

Case Study : If a weight hung from a string is made to swing, it always completes one to-and-fro motion in exactly the same time. In other words, it repeats the oscillation in equal intervals of time.
A simple pendulum consists of a weight (like small metallic ball or a piece of stone) tied to a string. The other end of the string is tied to a rigid support.
Fig. (a) shows the pendulum at rest in its mean position. When the bob of the pendulum is released after taking it slightly to one side, it begins to move to-and-fro [Fig. (b)]. The to-and-fro motion of a simple pendulum is an example of periodic and oscillatory motion.

Which of the following does not show periodic motion?

A A car moving at a constant speed
B Pendulum.
C Hands of a clock.
D Revolution of Earth around the Sun.


I marked A but it is showing it unattempted

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Daanish Nagpuria   from The HDFC School , Gurgaon
Subject :Physics    Class : Class 6

Case Study : When a piece of unmagnetised magnetic material touches or is brought near the pole of a permanent magnet, it becomes a magnet itself or we can say magnetism is induced. A north pole induces a north pole in the far end and vice versa. The induced magnetism is quickly lost when the magnet is removed from the magnetic field.

Which of these statements about magnetic induction is correct?

A Induced magnetism always make permanent magnets.
B Magnetic induction explains why an unmagnetised material may be attracted by a magnet.
C A material must touch the magnet to be induced.
D Magnetism can be induced in all the materials.


I didn't get the question and it's answer.

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Daanish Nagpuria   from The HDFC School , Gurgaon
Subject :Physics    Class : Class 6

Case Study : When a piece of unmagnetised magnetic material touches or is brought near the pole of a permanent magnet, it becomes a magnet itself or we can say magnetism is induced. A north pole induces a north pole in the far end and vice versa. The induced magnetism is quickly lost when the magnet is removed from the magnetic field.

Two iron needles hang from the end of a bar magnet, are inclined towards each other as shown in the diagram.

The reason for this is that __________.

A the needles are induced temporary magnets
B the ends of the needles are both north poles
C the ends of the needles are both south poles
D end of left needle is south pole and end of right needle is north pole.


Why can't it be d)?

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Daanish Nagpuria   from The HDFC School , Gurgaon
Subject :Physics    Class : Class 6

In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:
Assertion : One should not touch electrical appliances with wet hands.
Reason : Water is good conductor of
electricity.

A If both assertion and reason are true and reason is the correct explanation of assertion.
B If both assertion and reason are true but reason is not the correct explanation of assertion.
C If assertion is true but reason is false.
D If assertion is false but reason is true.


Water is a conductor, that is why we shouldn't touch it with wet hands.

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