# 7.4 Power  (Page 5/8)

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Consider a particle on which a force acts that depends on the position of the particle. This force is given by ${\stackrel{\to }{F}}_{1}=\left(2y\right)\stackrel{^}{i}+\left(3x\right)\stackrel{^}{j}.$ Find the work done by this force when the particle moves from the origin to a point 5 meters to the right on the x -axis.

A boy pulls a 5-kg cart with a 20-N force at an angle of $30\text{°}$ above the horizontal for a length of time. Over this time frame, the cart moves a distance of 12 m on the horizontal floor. (a) Find the work done on the cart by the boy. (b) What will be the work done by the boy if he pulled with the same force horizontally instead of at an angle of $30\text{°}$ above the horizontal over the same distance?

a. $208\phantom{\rule{0.2em}{0ex}}\text{N}·\text{m}$ ; b. $240\phantom{\rule{0.2em}{0ex}}\text{N}·\text{m}$

A crate of mass 200 kg is to be brought from a site on the ground floor to a third floor apartment. The workers know that they can either use the elevator first, then slide it along the third floor to the apartment, or first slide the crate to another location marked C below, and then take the elevator to the third floor and slide it on the third floor a shorter distance. The trouble is that the third floor is very rough compared to the ground floor. Given that the coefficient of kinetic friction between the crate and the ground floor is 0.100 and between the crate and the third floor surface is 0.300, find the work needed by the workers for each path shown from A to E . Assume that the force the workers need to do is just enough to slide the crate at constant velocity (zero acceleration). Note: The work by the elevator against the force of gravity is not done by the workers.

A hockey puck of mass 0.17 kg is shot across a rough floor with the roughness different at different places, which can be described by a position-dependent coefficient of kinetic friction. For a puck moving along the x -axis, the coefficient of kinetic friction is the following function of x , where x is in m: $\mu \left(x\right)=0.1+0.05x.$ Find the work done by the kinetic frictional force on the hockey puck when it has moved (a) from $x=0$ to $x=2\phantom{\rule{0.2em}{0ex}}\text{m}$ , and (b) from $x=2\phantom{\rule{0.2em}{0ex}}\text{m}$ to $x=4\phantom{\rule{0.2em}{0ex}}\text{m}$ .

a. $\text{−}0.9\phantom{\rule{0.2em}{0ex}}\text{N}·\text{m}$ ; b. $-0.83\phantom{\rule{0.2em}{0ex}}\text{N}·\text{m}$

A horizontal force of 20 N is required to keep a 5.0 kg box traveling at a constant speed up a frictionless incline for a vertical height change of 3.0 m. (a) What is the work done by gravity during this change in height? (b) What is the work done by the normal force? (c) What is the work done by the horizontal force?

A 7.0-kg box slides along a horizontal frictionless floor at 1.7 m/s and collides with a relatively massless spring that compresses 23 cm before the box comes to a stop. (a) How much kinetic energy does the box have before it collides with the spring? (b) Calculate the work done by the spring. (c) Determine the spring constant of the spring.

a. 10. J; b. 10. J; c. 380 N/m

You are driving your car on a straight road with a coefficient of friction between the tires and the road of 0.55. A large piece of debris falls in front of your view and you immediate slam on the brakes, leaving a skid mark of 30.5 m (100-feet) long before coming to a stop. A policeman sees your car stopped on the road, looks at the skid mark, and gives you a ticket for traveling over the 13.4 m/s (30 mph) speed limit. Should you fight the speeding ticket in court?

The displacement of the air molecules in sound wave is modeled with the wave function s(x,t)=5.00nmcos(91.54m−1x−3.14×104s−1t)s(x,t)=5.00nmcos(91.54m−1x−3.14×104s−1t) . (a) What is the wave speed of the sound wave? (b) What is the maximum speed of the air molecules as they oscillate in simple harmon
practical 1st year physics
huh
Luminous
Whats the formular for newton law of motion
f=ma
what is speed
distance travelled per unit of time is speed.
distance travelled in a particular direction it is.
Andrew
formula for velocity
v=ms^-1 velocity=distance time
Cleophas
(p-a/v)(v-b)=nrt what is the dimension of a
Amraketa
velocity= displacement time
Gold
what are evasive medical diagnosis?
If the block is displaced to a position y , the net force becomes Fnet=k(y−y0)−mg=0Fnet=k(y−y0)−mg=0 . But we found that at the equilibrium position, mg=kΔy=ky0−ky1mg=kΔy=ky0−ky1 . Substituting for the weight in the equation yields. Show me an equation of graph.
Shaina
simple harmonic motion defination
how to easily memorize motion equation
Maharam
how speed destrog is uranium
where can we find practice problems?
I'm not well
YAZID
Sayed
can u tell me the expression for radial acceleeation
No
YAZID
Is equal to the square of the velocity divided by the radius of circular path of the object
Mukhtaar
how to find maximum acceleration and velocity of simple harmonic motion?
chander
how to find maximum acceleration and velocity of simple harmonic motion and where it occurres?
chander
you can use either motion equations or kinetic equation and potential equation .
lasitha
how destraction 1kg uranium
Sayed
A Radial Acceleration is defined as the upward movement of an object.
Andrew
A body of 2.0kg mass makes an elastic collision with another at rest and continues to more in the original direction but with 1/4 of its ori is the mass of the struck body?
pls help me solve this problem
bright
why do sound travel faster in the night than in the day
I believe because speed is a function of air density, and colder air is more dense
Jerry
At night air is denser because of humidity.
Clifton
Night air is cooler. Sound requires medium to travel so the denser the medium the fastest the sound travels. Humid air is denser then warmer air as in day.
Clifton
The humidity statement is misleading , colder air is more dense period.
Jerry
because there is no any other sound to reverberate with it so it clearly travel to lot of distance and also humidity and also due to denser air at night
Azam
please could you guys help me with physics best websites
Baje
because it is quiet at night. this takes us to the topic wave, it depends on the wave at that moment, which Echo's....sound travelled.
Andrew
because it is quite at night. this takes us to the topic wave , it depends on the wave at that the physics
mehreen
element radioactivit diffusion atomic radius alpha beta gamma these elements have more than 92 atomic mass start from uranium
Sayed
please explain how alpha - beta
alpha discoved by ratherforth
Sayed
alpha discoved by Rutherford in 1899 have + charge and similarly to helium nucleus . When give 2 electron it change to helium nuclear( alpha + 2e = he
Sayed
bita has(-) charge it was also discovered by Ratherforth in 1899 (Bi = bita + po +gamma)
Sayed
Gamma is used to strength nuclear and out sametime with alpha and bita velocity 300000km/he discovered Biryquory in 1900 and more power influence then alpha and bita
Sayed
how mach destraction 1kg uranium
325
Mukhtaar
325km? or 365ft
Sayed