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You drop a ski glove from a height \(h\) onto fresh snow, and it sinks to a depth \(d\) before coming to rest. (a) In terms of \(g\) and \(h,\) what is the speed of the glove when it reaches the snow? (b) What are the magnitude and direction of the glove's acceleration as it moves through the snow, assuming it to be constant? Give your answer in terms of \(g, h,\) and \(d\).

Short Answer

Expert verified
(a) Speed when hitting snow is \( \sqrt{2gh} \). (b) Acceleration magnitude is \( \frac{gh}{d} \) upward.

Step by step solution

01

Identify Key Concepts

When the glove is dropped, it initially falls from rest. Therefore, we can use the concept of conservation of energy to find the speed when it hits the snow. Additionally, when the glove sinks into the snow at a constant acceleration, Newton's second law and kinematic equations can be used.
02

Use Conservation of Energy to Find Speed

Initially, the glove has gravitational potential energy given by \( PE = mgh \). As it falls, this potential energy is converted into kinetic energy: \( KE = \frac{1}{2} mv^2 \). By conservation of energy, \( mgh = \frac{1}{2} mv^2 \). Solving for \( v \), we find: \[ v = \sqrt{2gh} \].
03

Apply Kinematic Equation to Find Acceleration in Snow

Inside the snow, assume constant acceleration. The final speed within the snow is 0, the initial speed when hitting the snow is \( v = \sqrt{2gh} \), and the distance covered in snow is \( d \). Using the kinematic equation, \( v_f^2 = v_i^2 + 2ad \), set \( v_f = 0 \) and \( v_i = \sqrt{2gh} \): \[ 0 = (\sqrt{2gh})^2 + 2ad \] \[ 0 = 2gh + 2ad \] Solving for \( a \), we get: \[ a = -\frac{gh}{d} \].
04

Determine the Direction of Acceleration

The acceleration within the snow is negative relative to the direction of motion because it opposes the forward motion of the glove, bringing it to rest. Thus, the direction of acceleration is upward, opposing the descent of the glove.

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Key Concepts

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

Conservation of Energy
When you drop an object from a height, the energy transformation that takes place is critical in determining its speed upon impact. The principle of the conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. In the case of a falling glove, gravitational potential energy is transformed into kinetic energy. Initially, the glove at height \(h\) has potential energy \(PE = mgh\), where \(m\) is the mass of the glove and \(g\) is the acceleration due to gravity.
As the glove falls, this potential energy is converted to kinetic energy, given by \(KE = \frac{1}{2}mv^2\). By equating the initial potential energy to the kinetic energy just before impact, \(mgh = \frac{1}{2} mv^2\), and solving for \(v\), we find the speed of the glove at impact is \(v = \sqrt{2gh}\).
This concept is powerful because it allows us to calculate velocities without needing to know the time taken or the path of travel.
Constant Acceleration
When the glove hits the snow and starts to penetrate, it moves with a constant acceleration assuming uniform resistance from the snow. Constant acceleration means that the rate of change of velocity is uniform over time. In other words, the acceleration remains the same while the glove is sinking through the snow.
To derive such acceleration, we use kinematic principles. Given the initial velocity \(v_i = \sqrt{2gh}\), final velocity \(v_f = 0\), and distance \(d\) through the snow, the kinematic equation \(v_f^2 = v_i^2 + 2ad\) aids us in calculating acceleration \(a\). Solving the equation gives \(a = -\frac{gh}{d}\), indicating a constant uniform acceleration directly opposing the motion.
Newton's Second Law
Newton's Second Law lays the foundation for understanding how forces affect motion. It asserts that the acceleration of an object is directly proportional to the net forces acting upon it and inversely proportional to its mass (\(F = ma\)). This relationship is crucial in analyzing the glove's motion as it penetrates the snow.
While the glove is dropping, gravity accelerates it downward. Upon contact with the snow, however, a resistive force opposite to gravity acts upon the glove, leading to a constant deceleration. Here, the net force causes the glove to slow down, defined by the equation \(a = -\frac{gh}{d}\), where the negative sign indicates that the direction of acceleration opposes the motion of the glove. This interplay of forces is a real-world application of Newton's Second Law in a vertical motion scenario.
Kinematic Equations
Kinematic equations allow us to describe the motion of objects under constant acceleration without needing initial time information. These equations are crucial in solving problems involving motion along a straight path, like the glove moving through snow.
In this context, one specific kinematic equation \(v_f^2 = v_i^2 + 2ad\) helps ascertain the relationship between the initial velocity, final velocity, acceleration, and distance traveled. With our initial velocity as \(\sqrt{2gh}\), final velocity \(0\), and known distance \(d\), we solve to find \(a = -\frac{gh}{d}\).
This shows how kinematic equations provide insights into motion dynamics, bridging the link between velocity, acceleration, and distance in a cohesive manner.

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Most popular questions from this chapter

A hot-air balloon is descending at a rate of \(2.0 \mathrm{m} / \mathrm{s}\) when a passenger drops a camera. If the camera is \(45 \mathrm{m}\) above the ground when it is dropped, (a) how long does it take for the camera to reach the ground, and (b) what is its velocity just before it lands? Let upward be the positive direction for this problem.

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