1) A 4-kg mass moving with speed 2 m/s, and a 2-kg mass moving with a speed of 4 m/s, are gliding over a horizontal frictionless surface. Both objects encounter the same horizontal force, which directly opposes their motion, and are brought to rest by it. Which statement best describes their respective stopping distances?

(A) The 4-kg mass travels twice as far as the 2-kg mass before stopping. (B) The 2-kg mass travels twice as far as the 4-kg mass before stopping. (C) Both masses travel the same distance before stopping.

(D) The 2 kg mass travels greater than twice as far.
(E) None of the above

The correct answer is (B) The 2-kg mass travels twice as far as the 4 kg mass before stopping. To calculate the distance the object will slide one can use the work-energy theorem that states that the work done to a system is equal to the system's change in energy.

Here, the object starts with kinetic energy [KE = (mv^2)/2] and friction brings it to rest by doing an equivalent amount of work. Work is, in this case, the product of the force of friction and the distance the object slides while coming to rest. Therefore, the distance the object slides is directly proportional to the kinetic energy of the object, and inversely proportional to the force of friction, i.e. d = (mv^2)/(2F).

The 2-kg mass is half the mass of the 4-kg mass, and from this alone would have half of the kinetic energy as well. However, in this case the 2-kg mass is moving twice as fast as the 4-kg mass, and because its kinetic energy is dependent on the square of the velocity it turns out that the 2-kg mass has twice the kinetic energy of the 4-kg mass and will therefore slide twice as far before stopping.

2)A bird is standing in a bird cage, which is itself resting on an electronic balance. The bird flaps its wings and starts to fly upwards while remaining in the cage. Neglecting any effects from the turbulence of the air created by the flying bird, will the mass reading of the...

...Cosmology
By: Jarrett Leuta-Douyere
A New Look at Sports
Growing up in a family filled with athletic desire to be great at whatever sport we would participate in and understanding simple physics in Cosmetology, I never realized how much physics comes into play when playing sports. We don’t call it physics when were playing, football, basketball, baseball because it’s just a natural feeling when were throwing a ball or trying to tackle...

...We can relate physics to softball in many different ways. It is actually hard to not think about the game of softball without some physics in mind. Specifically, the ideas of momentum and energy helps define the way softball works and why it works.
Momentum
Running: When running the bases in softball, there is a lot more to it then the average person would think. While we run the bases, we are changing our momentum by applying more force, the force of friction,...

...
April 29, 2014
Abstract
The objective project was to use our knowledge of physic properties to create a working car that was powered by a mouse trap. I found that the lighter the car was and the more traction the car had, the further it travelled.
Introduction
The purpose of this project was to create a car that is powered by a mouse trap. We were to use our knowledge of physics laws to make the best car we can. I knew from Newton’s Law,...

...Name . . MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A freight car moves along a frictionless level railroad track at constant speed. The car is open on 1)top. A large load of coal is suddenly dumped into the car. What happens to the velocity of the car It remains the same. It increases. It decreases. cannot be determined from the information given 2) Tightrope walkers walk with a long flexible rod in order to 2) A) lower their...

...Student Exploration: Fan Cart Physics
Vocabulary: acceleration, force, friction, mass, newton, Newton’s first law, Newton’s second law, Newton’s third law, velocity
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Imagine a horse pulling a cart. What would happen to the speed of the cart if several bags of cement were added to the cart? The speed of the cart would decrease.
2. Suppose several more horses were hitched up to the same cart. How would...

...The Physics of Star Trek – Warp Speed
“Engage.” One simple command that triggers an entire series of complex reactions deep in the core and within the warp nacelles of the Starship Enterprise. Engage implied not only a command to fly off into the unknown reaches of space, but also a revolution of thinking that combined fundamental physics with the innovative ideas of the future.
Warp technology, as envisioned by the writers of Star Trek, can be linked to...

...PDP Physics Lab Report – 01
NAME: Wang Xueqian
DATE: 2014/06/21
Introduction
In this experiment, we will investigate the relationship between the linear speed of an object and magnitude of centripetal force acting on it. We will use a stopper moving in a circle to create an upward force on the hanging mass; at equilibrium, the upward force on the mass will exactly equal the centripetal force.
Apparatus
Two-hole Stopper
Plastic Tube
Plastic Clip
Electronic balance
Hooked...

...Patel Nil
Period 7
05/09/13
Static and Kinetic Friction
Objectives:-
* Use a Dual-Range Force Sensor to measure the force of static friction.
* Determine the relationship between force of static friction and the weight of an object.
* Measure the coefficients of static and kinetic friction for a particular block and track.
* Use a Motion Detector to independently measure the coefficient of kinetic friction and compare it to the previously measured value.
* Determine if...