Effects of forces on Solids and Liquids- IGCSE Physics

What is the correct equation for basic pressure 

• p = F / A

• p =  F x A

• p = A / F

Answer explanation

The correct equation for basic pressure is p = F / A, where p is pressure, F is force, and A is area. This formula shows that pressure is the force applied per unit area.

Which property of an object cannot be changed by a force?

• mass

• motion

• shape

• size

Answer explanation

Mass is a fundamental property of matter that does not change regardless of the forces applied. Unlike motion, shape, or size, which can be altered by external forces, mass remains constant.

What is the relationship between moment, force and distance? SELECT TWO CORRECT ANSWERS

• M = F x d

• M = F / d

• d = M x F

• F = M/d

Answer explanation

The moment (M) is calculated as the product of force (F) and distance (d), expressed as M = F x d. Rearranging this formula gives F = M/d, confirming both are correct relationships.

What is the moment acting on the seesaw?

• 1.6Nm

• 15Nm

• 16N

• 4Nm

Answer explanation

The moment on the seesaw is calculated as force multiplied by distance from the pivot. Given the correct answer is 1.6Nm, this indicates a specific force and distance combination that results in this moment.

The diagram shows a solid block resting on a bench. Teh dimensions of the block are shown.

On which labelled surface should the block rest to produce the smallest pressure on the bench?

• P

• Q

• R

• P, Q and R produce the same pressure.

Answer explanation

To produce the smallest pressure on the bench, the block should rest on the surface with the largest area. Surface P has the largest area compared to Q and R, thus resting on P minimizes pressure.

Which diagram shows an athlete exerting the least pressure on the ground?

• A

• B

• C

• D

Answer explanation

Diagram B shows the athlete with the largest surface area in contact with the ground, which reduces pressure. Pressure is calculated as force divided by area, so a larger area results in less pressure exerted.

A drawing pin (thumb tack) has a sharp point at one end and a flat surface at the other end.

The pin is pushed into a wooden board.

How do the pressure and the force at the sharp point compare with pressure and the force on the flat surface?

• Force at the sharp point is greater than on the flat surface

  AND
  pressure at the sharp point is greater than on the flat surface.

• Force at the sharp point is greater than on the flat surface

  AND
  pressure at the sharp point is less than on the flat surface.

• Force at the sharp point is same as on the flat surface

  AND
  pressure at the sharp point is greater than on the flat surface.

• Force at the sharp point is same as on the flat surface

  AND
  pressure at the sharp point is lass than on the flat surface.

Answer explanation

The force exerted by the pin is the same at both ends, as it is pushed with the same effort. However, the pressure at the sharp point is greater due to its smaller area, allowing it to penetrate the wood more easily.

A force acts on an area to produce a pressure. What changes produce the same pressure?

• double the area and double the force.

• double the area and halve the force.

• double the area and make the force four times bigger.

• Halve the area and double the force.

Answer explanation

Pressure is defined as force divided by area (P = F/A). Doubling both the force and the area keeps the ratio the same, thus maintaining the same pressure. Other options change the ratio, resulting in different pressures.

Identical toy bricks are placed one on top of another to make a tower on a table. Which graph shows the relationship between the pressure P that the tower exerts on the table and the weight W of the tower?

• 
• 
• 
• 

Answer explanation

The correct graph is the one with a straight line through the origin, increasing at a constant rate.

Here's why:

• Pressure is force per unit area. In this case, the force is the weight of the tower (W) and the area is the area of the base of the tower.

• As you add more bricks to the tower, the weight increases linearly.

• However, the area of the base remains constant.

• Therefore, the pressure (which is weight divided by area) also increases linearly with the weight.

• This relationship is best represented by a straight line through the origin, where the slope of the line represents the pressure per unit weight.

A vehicle sinks into soft ground. The vehicle has changed so that it does not sink as far. Which change is made?

• a lower centre of mass

• a more powerful engine

• wheels that are further apart

• wider tyres

Answer explanation

Wider tyres distribute the vehicle's weight over a larger area, reducing the pressure on the soft ground and preventing it from sinking as far. This is more effective than the other options listed.