# Search results

1. ### Stargazing Question on Refractor Telescope !

I am plan on building a small refractor telescope about 20 cm long, i need your guys help ! 1. What len is use for Objective len and what len is use for Eyepiece len ? (how is it look like) 2. How far should i place objective len and eyepiece len apart ? 3. If i make a 20 cm long refractor...
2. ### KE and PE Work

#1 A 10kg crate is pulled up a rough incline with an initial speed of 1.5 m/s. The pulling force is 100Nparallel to the incline, which makes an angle of 20* with the horizontal. If the coefficient of kinetic friction is .40 and the crate is pulled a distance of 5 m. a)HOw much work is done by...
3. ### Acceleartion and Force again !

#1 Ricky is on a rocket ship far from any planet or sun. The 900kg rocket fires its rockets for 3.5s sec and goes from 0m/s to 50 m/s.(a)What acceleration does the rocket undergo ?(b) If 160 kg of gas is expelled from the rocket. what is the gasses acceleration ? ------------------ vi = 50...
4. ### Acceleration coefficient

Find the acceleration experienced by each of the two masses shown in the picture below if the coefficient of friction between the 7 kg mass and the plane is .25 ? ------------ In the picture, is the force of fiction go that way ? http://img515.imageshack.us/img515/893/img3394dj7.jpg [Broken]...
5. ### Coefficient of friction of box of books

Problem 1: A box of books weighting 300 N is shoved cross the floor of an apartment by a force of 400 N exerted downward at an angle of 35.2* below the horizontal. If the coefficient of kinetic friction between box and floor is .57, how long does it take t move the box 4 m, starting from rest ...
6. ### Force - Scale - Tension

#1 On takeoff, the combined action of the engines and wings of an airplane exerts an 8000N force on the plane, directed upward at an angle of 65* above the horizontal. The plane rises with constant velocity in the vertical direction while continuing to accelerate in the horizontal direction...
7. ### What force ?

#1 A 5 g bullet leaves the muzzle of a rifle with a speed of 320 m/s. What force (assumed constant) is exerted on the bullet while it is traveling down the .82 m long barrel of the rifle ? -------------------------- m = .005 kg v (initial) = 320 m/s d = .82m F = ma but i don't know how to find...
8. ### Magnitude - Distance

[SOLVED] Magnitude - Distance #1 The force of the wind on the sails of a sailboat is 390 N north. The water exerts a force of 180 N east. If the boat (including crew) has a mass of 270 kg, what are the magnitude and direction of its acceleration. --------------------------------- 390 N...
9. ### The Law of Motion

An 850 kg car is moving to the right at 1.44 m/s. What is the net force on the car ? I am totally off on this problem ! Can someone help ? And in the problem above, it is different when the car moving left ? Thanks
10. ### 2 Projectile Motion Problem

#1 A bullet traveling 800 m/s horizontally hits a target 180 m away. How far does the bullet fall before it hits the target ? --------------------------------------- My work: X d = 180 m Vx = 180 m/s t = .225 s Y a = -9.8 m/s2 t = .225 s (time in x direction = time in y direction)...
11. ### Projectile Motion of a thrown stone

Homework Statement #1 A student stands at the edge of a cliff and throws a stone horizontally over the edge with a speed of 18 m/s. The cliff is 50 m above a flat horizontal beach. How long after being released does the stone strike the beach below the cliff ? With what speed and angle of...

Homework Statement #2 Two people pull on a stubborn mule, as seen from a helicopter in Figure 1. Find (a) the single force that is equivalent to the two forces shown, and (b) the force that a third person ould have to exert on the mule to make the net force equal to zero. Figure 1...
13. ### How long does it take ?

Homework Statement A hockey player is standing on his skates on a frozen pond when an opposing player, moving with a uniform speed of 12 m/s, skates by with they puck. After 3.0s, the first player makes up his mind to chase his opponent. If he accelerates uniformly at 4.0 m/s2. How long does...