Test: Force And Pressure - 4 - Class 8 MCQ

If we push or pull any object we use force to push or pull it. So... Force is both push and pull.

The strength of a force is expressed by its magnitude. The magnitude of a force is expressed in the SI unit of force called Newton. 1 Newton is the force which can make an object of 1 kilogram mass to move at a speed of 1 meter per second. The direction in which a force acts is also to be specified.

The force between two charged bodies is called:

- Electrostatic force.

Solution:
- The electric force between two charged bodies at rest is known as electrostatic force or Coulomb force.
- This force is described by Coulomb's law, which states that the magnitude of the electrostatic force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
- Electrostatic forces can be either attractive or repulsive depending on the nature of the charges involved.The electric force between two charged bodies at rest is conventionally  called electrostatic force or Coulomb force.

The state of rest or motion of an object is defined using a reference point. The reference point is a point used to describe the location of something. An object is said to be in motion, if it changes its position relative to the reference point. The mass, volume and size of the object are not necessary to describe whether the object is at rest or in motion.

Magnetic forces are non - contact forces;  they pull or push on objects without touching them. Magnets are only attracted to a few 'magnetic'  metals and not all matter.

Force is the push or pull activity on an object. It has the following properties : 1) Force can change the direction of a moving object. For example, we can change the direction of a moving ball by kicking it in another direction. 2) Force can change the shape of an object. For example, we can change the shape of a paper by crumbling it. 3) Force can change the speed by making a moving object move faster. For example, we can change the speed of a ball by kicking it. 4) Force can stop or slow down a moving object. For example, we can catch a falling ball and can thus stop it from falling. 5) Force can move an object in rest. For example, we can move a chair by pulling it.

Explanation:
Leaves or fruits fall on the ground due to gravitational force.
- Gravitational force is the force of attraction between two objects with mass. It is the force that pulls objects towards the center of the Earth.
- When leaves or fruits are detached from the tree or plant, the only force acting on them is gravity.
- Gravity pulls the leaves or fruits downwards towards the ground, causing them to fall.
- This is because all objects with mass are subject to the gravitational force, and the force is directly proportional to the mass of the object. Therefore, larger and heavier leaves or fruits are pulled down more strongly by gravity.
- The gravitational force also depends on the distance between the object and the center of the Earth. The closer an object is to the Earth's surface, the stronger the gravitational force.
- As a result, when leaves or fruits fall from the tree, they accelerate towards the ground under the influence of gravity until they reach the surface.
In summary, leaves or fruits fall on the ground due to the gravitational force, which is the force of attraction between objects with mass.

The force of friction is actually an example of a contact force, not a non-contact force. Friction occurs when two surfaces come into contact with each other and resist the relative motion between them.

Explanation:

When two forces act on an object in opposite directions, the net force on the object is indeed the difference between the magnitudes of the two forces. The direction of the net force will be in the direction of the larger force.

For example, if a force of 10 N acts to the right and a force of 4 N acts to the left on the same object, the net force will be:

The net force is 6 N to the right. Thus, the statement is true.

 The statement is incorrect because the force exerted per unit area is referred to as pressure, not magnitude. According to the NCERT textbook for Class 8 Science, Chapter "Force and Pressure," pressure is defined as the force applied per unit area on a surface. Therefore, the correct answer is option 2 (False).

If the force applied on the object is in the direction of its motion, the speed of the object increases. If the force is applied in the direction opposite to the direction of motion, then it results in a decrease in the speed of the object. Thus, a force may bring a change in the state of motion of an object. 

Gravity is a force that attracts objects towards each other. It is a non-contact force, meaning it does not require physical contact between objects for it to act. Instead, it acts over a distance.

Yes, at least two objects must interact for a force to come into play.

Force is defined as a push or pull that occurs between two objects. This interaction can happen in two ways:

• Contact: When the objects physically touch each other.
• Non-contact: When forces act at a distance, such as gravitational or magnetic forces.

In summary:

• For a force to exist, there must be an interaction between at least two objects.
• These interactions result in a force that can change the motion or shape of the objects involved.