What is the Average Pressure on an Apple During Impact?

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In summary, a 0.3 kg apple falls from rest through a height of 40 cm onto a flat surface. Upon impact, the apple comes to rest in 0.1 s, and 4 cm2 of the apple comes into contact with the surface during the impact. The average pressure exerted on the apple during the impact is 21,000 Pa, according to answer choice (B). This can be calculated by finding the velocity of the apple upon impact (2.83 m/s), the average force on the apple (8.48 N), and dividing that force by the surface area in contact with the surface (4 cm2).
  • #1
nhmllr
185
1

Homework Statement


1. A 0.3 kg apple falls from rest through a height of 40 cm onto a flat surface. Upon impact, the apple comes to rest in 0.1 s, and 4 cm2 of the apple comes into contact with the surface during the impact. What is the average pressure exerted on the apple during the impact? Ignore air resistance.
(A) 67,000 Pa
(B) 21,000 Pa
(C) 6,700 Pa
(D) 210 Pa
(E) 67 Pa
(the answer is b)

Homework Equations


p = mv
f = Δp/Δt
v = √(2gh)
pressure = force / surface area

The Attempt at a Solution


The velocity the apple is traveling at when it hits the ground is
v = √(2gh) = √(2* 10 * 0.4) = 2.83 m/s
The average force on the apple is
Δp/Δt = (0.3 * 2.83) / (0.1) = 8.48 N
So the average pressure on the apple should be
force/surface area = 8.48/(0.042) = 5300 Pa

But that is not an answer. What did I do wrong?
 
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  • #2
nhmllr said:

Homework Statement


1. A 0.3 kg apple falls from rest through a height of 40 cm onto a flat surface. Upon impact, the apple comes to rest in 0.1 s, and 4 cm2 of the apple comes into contact with the surface during the impact. What is the average pressure exerted on the apple during the impact? Ignore air resistance.
(A) 67,000 Pa
(B) 21,000 Pa
(C) 6,700 Pa
(D) 210 Pa
(E) 67 Pa
(the answer is b)

Homework Equations


p = mv
f = Δp/Δt
v = √(2gh)
pressure = force / surface area

The Attempt at a Solution


The velocity the apple is traveling at when it hits the ground is
v = √(2gh) = √(2* 10 * 0.4) = 2.83 m/s
The average force on the apple is
Δp/Δt = (0.3 * 2.83) / (0.1) = 8.48 N
So the average pressure on the apple should be
force/surface area = 8.48/(0.042) = 5300 Pa

But that is not an answer. What did I do wrong?

4 cm^2 is not the same as (4 cm)^2.
 
  • #3
Dick said:
4 cm^2 is not the same as (4 cm)^2.
...Whoops

Thanks
 

What is a simple pressure problem?

A simple pressure problem is a type of physics problem that involves calculating the pressure exerted by a fluid on a surface. This can include problems related to fluids at rest, such as a liquid in a container, or fluids in motion, such as a gas flowing through a pipe.

What is the formula for pressure?

The formula for pressure is P = F/A, where P is pressure, F is the force exerted on a surface, and A is the surface area. This formula can be used to calculate pressure in various units, such as Pascals (Pa) or pounds per square inch (psi).

How do you calculate the pressure in a liquid at a specific depth?

To calculate the pressure in a liquid at a specific depth, you can use the formula P = ρgh, where P is pressure, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the depth. This formula is based on the principle that pressure increases with depth in a liquid.

What is the difference between gauge pressure and absolute pressure?

Gauge pressure is the pressure measured relative to atmospheric pressure, while absolute pressure is the total pressure, including atmospheric pressure. In other words, absolute pressure = gauge pressure + atmospheric pressure. Gauge pressure is often used for practical purposes, while absolute pressure is used in scientific calculations.

How does temperature affect pressure?

As temperature increases, the pressure of a gas also increases. This is because the molecules in a gas move faster at higher temperatures, leading to more frequent and forceful collisions with the walls of a container, resulting in an increase in pressure. This relationship is described by the Ideal Gas Law: PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the gas constant, and T is temperature.

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