Force and Pressure - Free MCQ Practice Test with solutions, Class 8 Physics

Sharper tools exert more pressure because they have a smaller contact area. This high pressure makes it easier to cut through materials, as seen with knives and blades, which are designed with sharp edges to enhance their effectiveness.

According to Newton's second law of motion, force is defined as the product of mass and acceleration (F = m × a). This relationship shows how the force applied on an object is directly proportional to its mass and the acceleration it experiences.

The moment of force refers to the turning effect produced by a force when it is applied at a distance from a pivot point. It is calculated as the product of the force and the perpendicular distance from the pivot to the line of action of the force.

When thrust is applied to a soft surface, like loose sand, it causes the object to sink due to the smaller contact area exerting more pressure. This is why standing on sand can cause feet to sink more than lying down, which spreads the weight over a larger area.

Pressure is defined as the thrust (or force) applied per unit area. The formula for pressure is Pressure = Force / Area. This relationship helps in understanding how forces exerted over different areas can lead to varying pressure levels.

The S.I. unit of force is the Newton (N). One Newton is defined as the force required to accelerate a one-kilogram mass by one meter per second squared. This unit is named after Sir Isaac Newton, who is known for his laws of motion.

The moment of force is calculated using the formula Moment of Force = Force × Perpendicular Distance. Here, it would be 10 N × 2 m = 20 N·m. This calculation is essential in understanding how forces can cause rotation around a pivot.

Thrust is defined as the force that acts perpendicularly (normally) on a surface. It is essentially a push that can be exerted by an object due to its weight or any external force acting on it.

When a ball is tied to a point and pushed, it exhibits circular motion around that point. This occurs because the tension in the string or attachment constrains the ball to move along a circular path.

The S.I. unit for pressure is the Pascal (Pa), which is defined as one newton per square meter (N/m²). This unit is widely used in various scientific and engineering applications to quantify pressure levels.

Liquid pressure acts in all directions, not just downward. This property is crucial in understanding how liquids behave in containers and contributes to various applications, such as hydraulics.

Liquid pressure increases with depth due to the weight of the liquid above the point of measurement. This principle is used in applications such as designing dams and submarines to withstand high pressures at greater depths.

Sucking liquid through a straw is a practical application of liquid pressure. When you create a lower pressure inside the straw, atmospheric pressure pushes the liquid up into your mouth, illustrating how pressure differences work.

Pressure is inversely proportional to the area over which a force is applied. A smaller area results in higher pressure, while a larger area results in lower pressure. This principle explains why sharp objects can penetrate surfaces more easily than blunt ones.

The turning effect, or moment of force, is increased by applying a stronger force. Additionally, increasing the distance from the pivot also enhances the turning effect. Together, these factors determine how effectively a force can cause rotation.