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The weight of Santa Claus at the North Pole, as determined by a spring balance, is 875 \(\mathrm{N}\) . What would this spring balance read for his weight at the equator, assuming that the earth is spherically symmetric?

Short Answer

Expert verified
Santa's weight at the equator is approximately 873 N.

Step by step solution

01

Understand the Problem

The problem asks us to determine what Santa's weight would be at the equator using a spring balance, given that his weight at the North Pole is 875 N. We need to account for the difference in centrifugal force at the equator due to the Earth's rotation.
02

Calculate Gravitational Force

Santa's weight is the gravitational force acting on him. At the poles, this force equals his true weight: 875 N. Weight is the product of mass and gravitational acceleration, so we have: \[ W = mg \] where \( W \) is weight, \( m \) is mass, and \( g \) is gravitational acceleration. To find mass \( m \), we rearrange the formula: \[ m = \frac{W}{g} \] Using \( g = 9.81 \,\text{m/s}^2 \), solve for \( m \).
03

Consider Earth's Rotation at the Equator

At the equator, the effective gravitational force is reduced due to Earth's rotation. The centrifugal force is given by: \[ F_c = m \omega^2 R \], where \( \omega \) is the angular speed of Earth's rotation (\( 7.29 \times 10^{-5} \,\text{rad/s} \)), and \( R = 6.371 \times 10^6 \, \text{m} \) is Earth's radius. Calculate the centrifugal force \( F_c \).
04

Calculate Effective Gravity at the Equator

The effective gravitational force \( g_{eff} \) at the equator is \( g \) minus the centrifugal acceleration. Therefore: \[ g_{eff} = g - \omega^2 R \]. Substitute the known values to find \( g_{eff} \).
05

Calculate Weight at Equator

Calculate Santa's effective weight using the effective gravity at the equator obtained in the previous step:\[ W_{equator} = m \cdot g_{eff} \].
06

Conclusion

Combine all calculations to find Santa's weight at the equator and round to an appropriate number of significant figures.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Gravitational Force
Gravitational force is a natural phenomenon by which bodies with mass attract each other. On Earth, it gives us weight and holds everything down. Santa's weight at the North Pole is essentially the gravitational force acting on him at that point. This force is measured using a spring balance that reads 875 N. The gravitational force can be calculated using the formula: \[ W = mg \]where:- \( W \) is the weight,- \( m \) is mass, and- \( g \) is the gravitational acceleration (approximately 9.81 m/s² near the Earth's surface). This formula shows that weight depends on both mass and gravitational acceleration. At any location on Earth, you can determine the weight of an object by multiplying its mass by the gravitational acceleration at that point.
Centrifugal Force
Centrifugal force is an apparent force that acts outward on a body moving around a center, arising from the body's inertia. At the Earth's equator, this force affects how weight is perceived because it reduces the gravitational force slightly due to the Earth's rotation.In mathematical terms, centrifugal force is given by:\[ F_c = m \omega^2 R \]where:- \( F_c \) is the centrifugal force,- \( m \) is the mass,- \( \omega \) is the angular velocity of Earth's rotation,- \( R \) is Earth's radius.At the equator, the centrifugal force due to Earth's rotation decreases the effective gravitational force felt by Santa. This means that if Santa stands on a spring balance at the equator, his weight reading will be less compared to the North Pole.
Weight Calculation
Weight calculation involves determining how much gravitational force acts upon a mass. For Santa, whose weight at the North Pole is already known to be 875 N, we are interested in finding how this value changes at the equator. To find Santa's mass, we rearrange the weight formula:\[ m = \frac{W}{g} \]where:- \( W \) is the weight at the North Pole,- \( g \) is the gravitational acceleration.Once the mass is determined, Santa's weight at the equator is found by calculating the effective gravitational force:\[ W_{equator} = m \cdot g_{eff} \]where \( g_{eff} \) is the effective gravitational acceleration at the equator, accounting for both gravity and the reduced effect due to centrifugal force. This involves subtracting the centrifugal effect from the standard gravitational acceleration.
Earth's Rotation Effect
Earth's rotation has a subtle but significant effect on how we perceive weight. As the Earth spins, objects at the equator experience a centrifugal force, which effectively reduces the gravitational pull experienced on its surface.This effect can be described in terms of effective gravity:\[ g_{eff} = g - \omega^2 R \]where:- \( g \) is the acceleration due to gravity,- \( \omega \) is Earth's angular velocity,- \( R \) is the radius of the Earth.By subtracting the centrifugal acceleration from the gravitational acceleration, we find the effective gravity at the equator, \( g_{eff} \). This adjustment is necessary for accurate weight measurements at different latitudes, demonstrating how the Earth's rotation tangibly influences physical measurements.

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Most popular questions from this chapter

An experiment using the Cavendish balance to measure the gravitational constant \(G\) found that a uniform \(0.400-\mathrm{kg}\) sphere attracts another uniform \(0.00300-\mathrm{kg}\) sphere with a force of \(8.00 \times 10^{-10} \mathrm{N},\) when the distance between the centers of the spheres is 0.0100 \(\mathrm{m}\) . The acceleration due to gravity at the earth's surface is \(9.80 \mathrm{m} / \mathrm{s}^{2},\) and the radius of the earth is 6380 \(\mathrm{km}\) . Compute the mass of the earth from these data.

There are two equations from which a change in the gravitational potential energy \(U\) of the system of a mass \(m\) and the earth can be calculated. One is \(U=m g y\) (Eq. 7.2\()\) . The other is \(U=-G m_{\mathrm{E}} m / r(\mathrm{Eq} .12 .9)\) As shown in Section \(12.3,\) the first equation is correct only if the gravitational force is a constant over the change in height \(\Delta y .\) The second is always correct. Actually, the gravitational force is never exactly constant over any change in height, but if the variation is small, we can ignore it. Consider the difference in \(U\) between a mass at the earth's surface and a distance \(h\) above it using both equations, and find the value of \(h\) for which Eq. \((7.2)\) is in error by 1\(\% .\) Express this value of \(h\) as a fraction of the earth's radius, and also obtain a numerical value for it.

The star Rho "Cancri is 57 light-years from the earth and has a mass 0.85 times that of our sun. A planet has been detected in a circular orbit around \(R\) ho \(^{1}\) Cancri with an orbital radius equal to 0.11 times the radius of the earth's orbit around the sun. What are (a) the orbital speed and \((b)\) the orbital period of the planct of \(R h o^{1}\) Cancri?

The mass of Venus is 81.5\(\%\) that of the earth, and its radius is 94.9\(\%\) that of the earth. (a) Compute the acceleration due to gravity on the surface of Venus from these data. (b) If a rock weighs 75.0 \(\mathrm{N}\) on earth, what would it weigh at the surface of Venus?

(a) Asteroids have average densities of about 2500 \(\mathrm{kg} / \mathrm{m}^{3}\) and radii from 470 \(\mathrm{km}\) down to less than a kilometer. Assuming that the asteroid has a spherically symmetric mass distribution, estimate the radius of the largest asteroid from which you could escape simply by jumping off. (Hint: You can estimate your jump speed by relating it to the maximum height that you can jump on earth. (b) Europa, one of Jupiter's four large moons, has a radius of 1570 \(\mathrm{km}\) . The acceleration due to gravity at its surface is 1.33 \(\mathrm{m} / \mathrm{s}^{2}\) . Calculate its average density.

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