• Gravitation, Work and Energy
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Gravitation, Work and Energy

Description: All about work and energy
Number of Questions: 15
Created by:
Tags: Work Kinetic energy Potential energy Gravitation Thrust Definition of Work Work Kinetic Energy Potential Energy Gravitation Newton Law of Universal Gravitation Free Fall Conservation of Mechanical Energy Concept of Weight and Mass Thrust/ Pressure
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Work done by the potential energy of the object, which is above the ground is not ______________.

  1. directly proportional to the height from the ground

  2. directly proportional to the mass of the object

  3. inversely proportional to the height from the ground

  4. directly proportional to the gravitational force

  5. measured in joules

Show answer
Correct Option: C
Explanation:

Yes, it is correct as W is directly proportional to the height not inversely proportional. W = mass x gravity x height.

The force by which an object attracts other object is directly proportional to the product of their masses, is ___________________.

  1. the frictional force

  2. the gravitational force

  3. the magnetic force

  4. the thrust

  5. the pressure

Show answer
Correct Option: B
Explanation:

Yes, it is the gravitational force. Every object in the universe attracts other object by a force of attraction, called gravitation, which is directly proportional to the product of masses of the objects and inversely proportional to the square of distance between them.

Which of the following statements is false regarding the gravitational force?

  1. The planets revolve around the Sun in uniform motion due to presence of gravitational force.

  2. There is presence of atmosphere on the earth due to gravitational force.

  3. Tides in seas and oceans are due to gravitational force.

  4. It keeps the moon in orbit around the earth.

  5. None of these

Show answer
Correct Option: E
Explanation:

Yes, this is the correct answer as all the above statements are true. None of them is false regarding the gravitational force.

How does the gravitational force vary with the nature or properties of the medium in which the masses are placed?

  1. It remains constant

  2. It increases in a denser medium

  3. It decreases in a denser medium

  4. It becomes zero in rarer medium

  5. It becomes zero in denser medium

Show answer
Correct Option: A
Explanation:

Yes, it is the correct answer. The value of gravitational constant is same for any pair of masses in the universe but the value of G does not depend on the nature or properties of the medium in which the masses are placed. So, that is why the value of G is constant everywhere in universe.

If the displacement is perpendicular to the direction of the force, work done is ___________.

  1. positive

  2. negative

  3. zero

  4. can be either of three above options

  5. work cannot be done

Show answer
Correct Option: C
Explanation:

Yes, if the displacement is perpendicular to the direction of the force, work done is zero.

When is the work done said to be positive?

  1. If the body is displaced in the same direction of force.

  2. If the body is displaced and returns to same point.

  3. If the body is displaced in the opposite direction of force.

  4. If the body is not displaced.

  5. If the body is displaced, irrespective of the direction of force.

Show answer
Correct Option: A
Explanation:

Yes, if the body is displaced in the same direction of force, work done is positive.

Which of the following object /s possess kinetic energy? (a) Bullet fired from a gun (b) Weight kept at a height (c) Hammer striking a nail (d) Water in an overhead reservoir

  1. Both a and c

  2. Both b and d

  3. Only a

  4. Only c

  5. Only d

Show answer
Correct Option: A
Explanation:

Yes, here the objects possess kinetic energy. Energy possessed by an object due to its motion is called kinetic energy. The bullet and the hammer.

Which of the following is true about free fall?

  1. Object falls under the influence of gravity.

  2. Fall of parachute towards Earth.

  3. Free fall is independent of the mass of object falling.

  4. Option 1 and 2.

  5. Option 1 and 3.

Show answer
Correct Option: E
Explanation:

Yes, it is correct as both 1 and 3 are true.

A ball is falling down from a height of 20 cm. What type of energy will it possess, when it will be at 12 cm?

  1. Potential energy

  2. Kinetic energy

  3. Both kinetic energy and potential energy

  4. It is a free fall so energy will be zero. Hence, there will be no energy

  5. It is a free fall so energy will be equal to gravity. Hence, gravitational energy

Show answer
Correct Option: B
Explanation:

Yes, it will possess kinetic energy as the ball is still in motion.

An object weighs W, when on earth. What will be its weight , when on the moon?

  1. Same

  2. Six times W

  3. 1 / 6 times of W

  4. Zero

  5. Will depend on the material of the object

Show answer
Correct Option: C
Explanation:

Yes, it is the correct answer. Weight of an object on the moon = 1 / 6 of the weight of the object on earth.

An object has M mass, when on earth. What will be its mass, when on moon?

  1. Same

  2. Less than M

  3. More than M

  4. Zero

  5. Will vary with the material it is made up of

Show answer
Correct Option: A
Explanation:

Yes, mass of an object remains constant everywhere, i.e. mass will remain same whether that object is at the moon, at the earth or anywhere in the universe.

What will be the mechanical energy of an object, if it has momentum equal to zero?

  1. Zero

  2. Equal to its kinetic energy

  3. Equal to its potential energy

  4. greater than potential energy.

  5. None of these

Show answer
Correct Option: C
Explanation:

Yes, it is correct. Momentum is zero which means velocity is zero. Hence, there is no kinetic energy but the object may possess potential energy.

Why do tractors run easily on loose agricultural fields?

  1. Its engine is stronger

  2. Its body is stronger

  3. Its wheels are broader

  4. Its wheels are frictionless

  5. It is easily available in villages

Show answer
Correct Option: C
Explanation:

Yes, because of broader tyres, a tractor exerts less pressure over the ground as pressure decreases with increase in surface area or contact, and hence easily runs over the muddy field.

When a nail is pushed in a wall or wood, it is pushed from pointed side. Which of the following is the correct reason behind this?

  1. Pointed end cuts the wall or wood as it is sharp.

  2. Because of pointed shape, nail exerts more pressure over the wall or wood and is easily pushed by hammering.

  3. Because we cannot hold it from the pointed end, therefore keep it towards the wall or wood.

  4. Pointed end has concentrated metal, hence is stronger.

  5. All of these

Show answer
Correct Option: B
Explanation:

Yes, because of pointed shape, nail exerts more pressure over the wall or wood and is easily pushed by hammering. Pressure increases with decrease in surface area and decreases with increase in surface area.

Which of the following object does not possess potential energy?

  1. A roller coaster on the top of a hill track.

  2. A rocket ready for takeoff.

  3. Boiling of liquid nitrogen.

  4. A lady resting on bed.

  5. A snowball on top of a snowy mountain.

Show answer
Correct Option: C
Explanation:

Yes, it is an example of kinetic energy.

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