Motion & Forces - Chapter 3

The unit used to measure pressure is the Pascal (Pa). Pressure is defined as the force applied per unit area, and the Pascal is the SI unit for measuring this. It is named after the French mathematician and physicist Blaise Pascal. The Pascal is equivalent to one Newton per square meter (N/m^2), which represents the amount of force exerted on a surface area of one square meter.

The resistance that Michelle feels while sliding the box across the floor is caused by friction. Friction is the force that opposes the motion of two surfaces in contact with each other. In this case, the box and the floor are in contact and the friction between them resists the motion of the box, making it harder for Michelle to push it.

When Robin fills the cart with rocks, the mass of the cart increases. According to Newton's second law of motion, the force required to move an object is directly proportional to its mass. Therefore, as the mass of the cart increases, Robin's force needs to be greater in order to push the more massive cart at the same steady speed.

The pressure exerted when a force of 50N is applied to a box with an area of 4 meters squared is 12.5 Pa. This is calculated using the formula for pressure, which is P = F/A. In this case, the force is 50N and the area is 4 meters squared. Therefore, the pressure is 50N/4m^2 = 12.5 Pa.

In the water, Melanie can lift her little brother easily because of the buoyant force. When an object is submerged in a fluid, it experiences an upward force called buoyant force, which is equal to the weight of the fluid displaced by the object. This buoyant force counteracts the force of gravity, making it easier for Melanie to lift her brother in water compared to on land.

To minimize air resistance, Roger should decrease the surface area of the model rocket. This is because air resistance is caused by the friction between the rocket and the air molecules it encounters. By reducing the surface area, there will be less contact between the rocket and the air, resulting in less friction and thus less air resistance.

As Lisa climbs a mountain, the air pressure relative to sea level decreases. This is because as she gains altitude, the weight of the air above her decreases, resulting in lower air pressure. Therefore, there is more air below her than above her.

The correct answer is to divide the force by the area over which it is exerted. This is because pressure is defined as the force applied per unit area. By dividing the force by the area, we can determine the amount of force exerted on each unit of area, which gives us the pressure.

After a space shuttle is launched into orbit, gravity continues to pull it toward the center of Earth. This is because gravity is a force that attracts objects with mass towards each other. Even though the shuttle is moving at a high speed in orbit, the gravitational force is still acting on it, constantly pulling it towards the center of the Earth. This force is what keeps the shuttle in its orbit and prevents it from flying off into space.

The tennis ball will hit the ground first because it has a smaller surface area, which means it will experience less air resistance compared to the larger basketball. This allows the tennis ball to fall faster and reach the ground before the basketball.

In a vacuum, there is no air resistance to affect the motion of the balls. This means that the only force acting on both the hollow plastic ball and the solid metal ball is gravity. According to the law of universal gravitation, all objects experience the same acceleration due to gravity regardless of their mass or size. Therefore, both the hollow plastic ball and the solid metal ball will fall at the same rate.

By putting a plastic sheet on the floor before sliding the chair, Mark can reduce the effect of friction. The plastic sheet creates a smooth surface, which reduces the friction between the chair and the carpet. This allows the chair to slide more easily across the floor.

Box A exerts the greatest pressure because pressure is defined as force divided by area. Since both boxes have the same area on the floor, the force exerted by the boxes will determine the pressure. Since Box A has a larger area, it will exert a greater force on the floor compared to Box B, resulting in a greater pressure.

When Naomi squeezes the wide end of the toothpaste tube, the pressure she exerts is transmitted equally to the opposite end of the tube. This is because the toothpaste inside the tube is incompressible, meaning that any pressure applied to one end of the tube will be transmitted throughout the entire volume of toothpaste. Therefore, the pressure transmitted to the opposite end of the tube is equal to the pressure Naomi exerts.

Gravity is the force that attracts two masses to each other. It is a fundamental force in nature that acts between all objects with mass. Unlike air resistance, friction, and pressure, which are forces that arise from interactions with specific substances or surfaces, gravity is a universal force that affects all objects in the universe.

Bernoulli's principle states that as the speed of a fluid increases, its pressure decreases. In the case of a fast-moving stream, the water flows quickly, resulting in a decrease in pressure on the bottom. This is because the fast-moving water has a lower pressure compared to the slower-moving water. Therefore, the correct answer is Bernoulli's principle.