Tag: contact and non-contact forces

Questions Related to contact and non-contact forces

Does moon have its own gravity?

physics primary concept of force and energy contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. No

  2. Yes

  3. Not known yet

  4. Only during full moon

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Correct Option: B
Explanation:

Gravity is not a property of the earth alone. Every object in the universe exerts a force on every other object. This is called gravitational force. Naturally, moon also has its own gravity.

Which of the following is the weakest force?

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. Nuclear force

  2. Gravitational force

  3. Electromagnetic force

  4. None of these

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Correct Option: B
Explanation:

Answer is B.

Gravity is a very, very weak force. In a hydrogen molecule it pulls the two protons together with a force about 36 powers of ten weaker than the electric force between them.
Therefore, on small scales (within an atom/molecule), the other forces are much stronger, but on larger scales, it seems that gravity is a far stronger force; e.g. planets are held to the sun by gravity. 
Hence, among the given options, gravitational force is the weakest.

There are circumstances in which two objects exert forces on one another even though they are not touching. Such forces are called (Mark the most appropriate answer)

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. non-contact forces

  2. contact forces

  3. electric forces

  4. attractive forces

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Correct Option: A
Explanation:

A non-contact force is a force applied to an object by another body that is not in direct contact with it. The most familiar example of a non-contact force is weight.

It is easier to drive a screw rather than a nail of the same size into a wall because:

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. The nail moves a larger distance for the same force applied

  2. The screw moves a larger distance for the same force applied

  3. The direction of force applied in the screw is perpendicular to its movement

  4. The screw acts as a wedge

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Correct Option: C
Explanation:

In screws the direction of force applied is perpendicular to the wall and due to its cuts present their is a force applied tangential to the wall which helps in easy movement of the screw.

Which of the following is a non contact force?

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. muscular

  2. electrostatic attraction

  3. elastic spring force

  4. friction force

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Correct Option: B
Explanation:

Coulomb electrostatic force of attraction acts between the two bodies which are separated by a finite distance, hence it is non contact force since the two bodies need not to be in contact with each other whereas the rest of the forces are contact forces.

Let E,G and N represents the magnitude of electromagnetic, gravitational and nuclear forces between protons and electrons at a given separation (1 fermi meter). Then

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. N < E < G

  2. E > N > G

  3. G > N > E

  4. N > E > G

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Correct Option: D
Explanation:

$r=1fermimeter$ which is same for all.
$F _e=\frac{k _eq _1q _2}{r^2}  ;F _g=\frac{Gm _1m _2}{r^2}$ ; 
$F _N=\frac{\alpha}{r^2}$
where$k _e=8.988\times10^9 N^2m^2c^{2} $;
$q _1=-1.6\times10^{-19}c$; 
$q _2=1.6\times10^{19}$;
$G=6.67\times10^{-11}m^3kg^{-1}s^2$;
$m _1=9.1\times10^{-31}kg$; 
$m _2=1.67\times10^{-27}kg$;
$\alpha=2.3103\times10^{-28}$
$F _e=2.307\times10^{-28}$  ; ${F _g}=1.868 \times10^{-64}$ ;
$F _N=2.3103 \times10^{-28}$
hence,$F _N>F _e>F _g$


State True or False :
Magnetic force attracts all kinds of metals. 

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. True

  2. False

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Correct Option: B
Explanation:
Magnetic force only attracts metals, which are ferromagnetic. Not all metals are ferromagnetic.

State True or False :
Gravity of Earth, attracts all objects towards the centre of Earth.

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. True

  2. False

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Correct Option: A
Explanation:

The Earth is one massive object whose gravitational force is very strong. Thus gravity of Earth attracts all objects towards the centre of Earth.

State whether the given statement is true or false :
Gravity and friction are both contact forces. 

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. True

  2. False

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Correct Option: B
Explanation:

Answer is B.

The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth. 
The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. There are three types of frictional force - sliding and static friction. Though it is not always the case, the friction force often opposes the motion of an object. 
Hence, gravity is a non-contact force and friction is a contact force.

Gravitational force acts

physics motion, force and speed contact and non-contact forces comparing force in magnetic, electric and gravitational fields identifying forces

  1. only between the sun and the planets moving around it.

  2. only between the earth and the bodies on it.

  3. between all bodies in the universe.

  4. only between the Sun and the earth.

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Correct Option: C
Explanation:

Answer is C.

The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. Gravitational force exists between all the bodies having mass in the universe.