# Search results

1. ### Energy and basic math (proportionality)

Homework Statement A person running in a race has to pick up a mass equal to her own mass. Assuming she can still do the same amount of work, her speed will be changed by a factor of a. 0.25 b. 0.50 c. 0.71 d. 1 e. 2 Homework Equations E=1/2mv2 The Attempt at a Solution Since m is...
2. ### Calculating Distance Given Work and Forces

Homework Statement A farmhand does 972 J of work pulling an empty hay wagon along level ground with a force of 310 N [23 degrees below the horizontal]. A frictional force of 280 N opposes the motion. The distance the wagon travels is a. 0.39 m b. 1.7 m c. 3.4 m d. 32 m e. 1.8 x 102 m Homework...
3. ### Sum of Infinite Series

I'm not sure which category this post actually belongs to, or if the title of this post is even accurate. I guessed Calculus was the closest one. I watched this video on the web after a professor told me this mathematical phenomenon (http://www.youtube.com/watch?v=w-I6XTVZXww‎). It asserts...
4. ### Three girls pull a sled. Determine the acceleration.

Homework Statement Two girls pull a sled across a field of snow, as shown in the diagram. A third girl pulls backward with a 2.0 N force. If the mass of the sled is 10 kg, determine its instantaneous acceleration. Homework Equations F=ma The Attempt at a Solution Sorry, I'm stumped.
5. ### Football Vector Motion Problem

Homework Statement A quarterback is running across the field, parallel to the line of scrimmage, at a constant speed of 2.5m/s, when he spots an open, stationary receiver straight downfield from him (ie, in a line parallel to the sidelines). If he can throw the football at a speed of 8.0m/s...
6. ### Find the displacement in a word problem

Homework Statement A car is slowing down at a rate of 20 km/h/s. How far does it travel if its original velocity is 50 km/h and its final velocity is 5.0 m/s? Homework Equations vf2 = v02 + 2aΔx The Attempt at a Solution vf2 = v02 + 2aΔx Δx = (vf2 - v02) / 2a = (182-502) /...
7. ### Word Problem with Kinematics Equation

Homework Statement An object thrown up from a cliff 10 m/s reaches a velocity of 20 m/s [down] as it lands. If acceleration due to gravity is 9.8 m/s2, what is the object's displacement? How long did it take for the object to land from the time it was thrown? Homework Equations I'm not...
8. ### Average Speed vs. Instantaneous Speed

Homework Statement A book falls off a shelf and lands on the floor. Which is greater, the book's average speed or its instantaneous speed right before it lands? Homework Equations v = d/t The Attempt at a Solution I think its the instantaneous speed because the book accelerates...
9. ### Movement at Absolute Zero

Is it possible for motion to exist at 0 Kelvin?
10. ### Cheap Piezoelectric Generator

With a budget of less than \$100, does anyone have an idea on how to make a cheap piezoelectric generator using materials found at home? (aluminum foil, wire, battery, and a silicon swim cap maybe?) I plan to modify this generator to then integrate it inside a bike tire so that whenever I ride...
11. ### Can magnets defy the law of energy conservation?

I'm pretty sure it cannot, but if I put a common bar magnet close to another magnet, they will move towards each other. I don't have much of a background in physics, but it seems to me that the kinetic energy is coming out of...nowhere. I can repeat this experiment as many times as I like but...
12. ### Confused with the Archimedes' Principle

Archimedes' Principle states: "Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object." If this is true, why then, when you take a bowling ball and submerge it in water, and take a rubber ball of the same size and...
13. ### Algebraic Expression

Homework Statement In this pattern, what is the algebraic expression for the term t? -15, 30, 90, -360 Homework Equations t= term number The Attempt at a Solution no idea
14. ### How photon entanglement works?

How do you get photos to become entangled? And is this even possible, or just a theory?
15. ### Immediate Acceleration Possible?

Is it possible that an object changes velocity immediately? For example, Object A is ALWAYS travelling at a constant velocity (say 100mph). Its velocity never changes. If Object B (which is at rest) were in the path of Object A and Object A were to slam into Object B, would Object B...
16. ### Earth, Sun, Moon Orbit

Why does the Earth orbit the Sun, but the Moon pull on Earth's tides? Earth orbits the sun, proving that the Sun has a greater gravitational pull on the Earth than the Moon. However, the Moon control's Earth's tides (unlike the Sun), which proves the opposite-the Moon has a greater...