Test: Force- 2 - EmSAT Achieve MCQ

• Surface tension is the property by virtue of which liquid tries to minimise its free surface area.
• In spherical shape the surface area is minimum and for this reason, the raindrops are spherical.
• Two factors can affect the surface tension of a liquid. The factors are;
  • Temperature: If temperature increases then the surface tension of a liquid decreases. At the critical temperature the surface tension becomes zero.
  • Soluble Impurities: In the case of less soluble impurities, the surface tension decreases. But, for highly soluble impurities in the liquid the surface tension increases.
• Examples:
  • When kerosene oil is sprinkled on the water the surface decreases and for this reason, the mosquito larvas die due to sinking in the water.
  • Warm soup is tasty because for high temperature the surface tension becomes low and spread equally over the tongue.
  • The surface tension of antiseptics is low that the reason they reach in the small cracks of the wound and cleans the germs.
  • The surface tension of soap solution is less than the pure water and for this reason, the soap solution cleans clothes better than pure water.

• It is almost impossible to predict the earthquake, though the earthquake-prone areas can be predicted.
• Such areas have frequent tremours of low magnitude and much less frequent earthquakes.  
• The use of heavy construction materials is not recommended for such areas. 
• The heavy structure when fall, will cause much damage to life and property. 
• It is better to use mud or timber with light roofs as a design criterion for making houses in earthquake-prone areas. 
• Use of attached cupboards (attached with the wall) are good to use as they will not fall with small tremors of the earthquake. 
• Some buildings may catch fire due to the fall of electric poles or other reasons, thus the use of Fire extinguishers would be helpful.

So, the correct option is 'Use of heavy construction materials.'

• Thrust is the force that moves an aircraft through the air.
• Thrust is used to overcome the drag of an airplane, and to overcome the weight of a rocket.

• A car towing another car with a chain is an example of a Tension force.
• The force of tension is defined as the force which is transmitted by rope, string, or wire when pulled by forces acting from opposite sides.
• The force of stress is directed over the length of the wire and at the ends pulls energy evenly on the bodies.
• Any physical object that is in contact with each other exerts some force.
• Cables and ropes can be used to exert forces since they can easily move a force over a given distance (e.g. the length of the rope). 

Given data -

Mass, m = 40 kg
Height, h = 5m

Time, t = 4s

Work done, W = mgh
W = 40 × 10 × 5 [g = 10 m/s2, given]

W = 2000 joules

→ Power, P = work done /time

P = 2000/4

P = 500 joule/sec

P = 500 W

• This constant tug on the Moon as it moves around the Earth is called a "centripetal" force. This force is balanced by the "centrifugal" force, that pulls on the Earth and keeps the moon in motion.
• The moon revolves around earth because of Earth’s gravitational force.
• The Gravitational force of Earth tends to attract Moon.
• The centripetal force acts on a body, moving in a circular path, and is directed towards the center around which the body is moving.

The correct answer is option 2 i.e. Gravitational force.

• All objects in the universe attract each other. This force of attraction between objects is called the gravitational force.
• The attractive or repulsive forces between particles or objects due to their electric charges is known as electrostatic force.
• The force resulting due to the action of muscles is known as the muscular force; since it can be applied only when it is in contact with an object, it is also called a contact force.
• The force of attraction or repulsion that arises between electrically charged particles because of their motion is known as a magnetic force.

In science, a push or a pull on an object is called force.

The correct answer is Magnetic Force.

• Forces can be broadly categorized into two types: contact forces and non-contact (or action-at-a-distance) forces.
• Contact forces require physical interaction between objects, whereas non-contact forces act over a distance without direct physical contact.
• Magnetic force is a force that arises due to the magnetic field generated by magnets or moving electric charges.
• It can act over a distance, attracting or repelling objects without requiring physical contact.
• Therefore, magnetic force is a clear example of a non-contact force.

• A cannon after firing recoils due to Newton's Third law of motion.
• Newton's Third Law: For every action, there is an equal and opposite reaction.
• Some of the examples of Newton 3rd Law are Gun Firing in which when someone fires a gun the reaction force pushes the gun backward or When a rocket tool flight, it exhausts the gas from its back. The reaction force pushes the rocket upward.
• Law of Conservation of Energy: Energy can neither be created nor be destroyed.
• Newton's First Law of Motion: Every object persists in its state of rest or in uniform motion in a straight line unless it is compelled to change that state by forces impressed on it. This law is also known as the Law of Inertia.