# Recently Submitted Homework Problems: physics

113. What is the difference between a scalar and vector quantity?(Answered)127. What is law of motion?(Answered)

139. Please help on this question:-

A particle is trapped in an infinite one-dimensional well of width 0.132nm. The electron is in the n=10 state. A) What is energy of the electron? B) What is the uncertainty in its momentum?(Answered)

142. what is the dimension of amount of a substance(Answered)

186. a 925 N crate is being pushed across a level floor by a force of 325 N at an angle of 25 degrees above the horizontal. The coefficient of kinetic friction is 0.25. Find the magnitude of the acceleration of the crate.(Answered)

349. A rope having a total mass of 0.4kg and total length 4m has 0.6m of the rope hanging vertically down off a work bench. How much work must be done to place all the rope on the bench?(Answered)

1239. help me solve this physics problem: A 5.0 block is dropped from a height of 19.6 how much power is supplied by gravity in bringing the block to the ground?(Answered)

1239. help me solve this physics problem: A 5.0 block is dropped from a height of 19.6 how much power is supplied by gravity in bringing the block to the ground?(Answered)

568. 2) A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass

with respect to the ground? c

2)

A) 80 J

B) 32 J

C) 8 J

D) 6 J

E) none of these

Topic: Energy

(Answered)

826. suppose a beam of 5ev strikes a potential energy barrier of height 6ev and thickness 7nm at a rate equivalent to a current of 1000A. How long would you have to wait on average for one proton to be transmitted?(Answered)

1381. When do we say that a body is a rest and when do we say that it is moving ?(Answered)

1478. Suppose you want to make a scale model of a hydrogen atom. You choose for the nucleus a small ball bearing with a radius of 2mm.The radius of the hydrogen atom is 0.529x10^-10 m and the radius of the nucleus is 1.2 x 10^-15m. What would the radius of the model be in m?

Suppose that you now want to make a scale model of the solar system using the same ball bearing to represent the sun. How far from it in mm would you place a sphere representing the earth? (Earth is 1.496 x 10^11m from the sun)

(center to center distance)

And, what would be the radius (mm) of the sphere representing the earth?(Answered)

1496. The supermarket tabloids report that a person fell 130ft from a bldg. He landed on a ventilator box which was crushed 18.7 in. Use a coordinate system with down being + to answer. What is his speed (m/s) before colliding with the box? What is his acceleration (m/s/s) while crushing the box (assume constant acc.)? How long did it take (ms) for him to come to a stop after first contacting the box?(Answered)

1508. A rancher sits on a tree limb and drops vertically onto a galloping horse under the tree. The speed of the horse in 9.28m/s and the distance from the limb to the saddle is 3.23m. What must be the horizontal distance in m between the saddle and the limb when the rancher drops and how long (s) is he in the air?(Answered)

1534. two air carts of mass m1=0.84kg and m2=0.42kg are placed on a frictionless track. Cart1 is at rest and has a spring bumperwith a constant force of 690N/m. cart2 has a metal surface bumper and moves towards cart1 with a speed V=0.68m/s.(1) what is the speed of the two carts at the moment when their speeds are equal?(2)how much energy is stored in the spring bumper when the carts have the same speed?(3) what is the final speed of the carts after the collision?(Answered)

1845. A hot air balloon rose from a height of 100m to 400m in 3 minutes. What was the balloon's rate of change (Answered)

1847. 007 10.0 points

A basketball player achieves a hang time of

0.506 s in dunking the ball.

What vertical height will he attain? The

acceleration of gravity is 9.8 m/s2 .

Answer in units of m(Answered)

1863. A 15-foot-long car going 60 mph is passing a 30-foot-long truck going 50 mph. How much time will it take for the car to move from position (a), where the front of the car is even with the back of the truck, to position (b), where the back of the car is even with the front of the truck? (If you have a textbook, the picture for 1.6 #70 shows this situation.) Give your answer in seconds, rounded to the nearest tenth of a second. [Hint: you will have to do some unit conversions. 1 mile = 5280 feet. I assume everyone knows how many seconds are in a minute and minutes in an hour.](Answered)

1893. A car traveling 89 km/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.94 m.

What was the average acceleration of the driver during the collision? (Answered)

1893. A car traveling 89 km/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.94 m.

What was the average acceleration of the driver during the collision? (Answered)

1894. A car traveling 89 km/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.94 m.

What was the average acceleration of the driver during the collision?

Express the answer in terms of "{\rm g}'s," where 1.00\,{\rm g} = 9.80\;{\rm{m/s}}^2. (Answered)

1933. what equation do i use to find how much space a car needs to increase its velocity

(Answered)

1943. On the moon, an object is dropped from a height of 2 m. The acceleration of gravity on the moon is . Determine the time it takes for the object to fall to the surface of the moon.(Answered)

1961. If you dropped your textbook from the top of a 15 storey, building how long will it take the textbook to reach the bottom? Each storey is 3.0m and gravity=9.8m/s^2

(Answered)

2081. What is the period that corresponds to a

frequency of 53.1 Hz?

Answer in units of s (Answered)

2126. what is center of mass(Answered)

2129. What is Black Hole?(Answered)

2283. Can you help me with this physics problem? A box starting from rest is pulled by means of a rope which make an angle of 30 degrees with the horizontal. If the box travels a distance of 10.0m in 2.0 sec, what is the magnitude of the force exerted by the rope? The mass of the box is .50 kg(Answered)

2664. A knight sits on a castle wall during a siege. To while away the time, he notes that boulders catapulted from below land on the top of his wall with a vertical velocity of 9.4 m/s. If he is 28 m above the catapult, what is the initial velocity of the boulders? The acceleration of gravity is 9.8 m/s^2. Answer in units of m/s.(Answered)

2807. a sample of radium -226 has half life of 4 days. find the probability,a nucleus disintegrates within 2 half lives(Answered)

3050. To push a certain box across a level floor at constant velocity requires that a horizontal force be applied to the box. The magnitude of this force is half as great as the vertical force required to lift the box. Find the coefficient of kinetic friction between box and floor.(Answered)

3236. a) Research the space elevator and describe how the rotation of the earth prevents the cable from falling to its attachment point at the earth's equator.

b) Consider the environment in which the cable must operate. Recommend two

physical, and one chemical property that the cable should have. Justify your

choices.

c) Based on what you have learned about bonding in solids, which type of solid, in your opinion, is the most suitable for use in the space elevator cable? Justify your choice.

d) Research which technical hurdles must be overcome before your choice in (c) can be used for the elevator cable.

(Answered)

3427. A light string of length a is attached to two points A and B on the same level and distance b apart, where b < a. A smooth ring of weight W is threaded on the string and is pulled by a horizontal force P, so that it rests in equilbrium vertically below B. Show that tension in the strings is W(a^2 + b^2)/2a^2 and find the force P (Answered)

3495. Ammonia weighing 22 kg is confined inside a cylinder equipped with a piston has an initial pressure of 413 kPa at 38 Celsius. if 2900 kJ of heat is added to the ammonia until its pressure are 413 kPa and 100 Celcius, respectively. what is the amount of work done by the fluid in kJ?(Answered)

3610. The man pulls on the rope with a force of 60 lb. If F acts within the octant

shown, such that a=45 and b=60 determine the x, y, z components of F.(Answered)

3867. can you help me define constant acceleration?

(Answered)

3867. can you help me define constant acceleration?

(Answered)

4086. When a small 2.0 g coin is placed at a radius of 5.0 cm on a horizontal turntable that makes three full revolutions in 3.14 s, the coin does not slip. What are (a) the coin's speed, the (b) magnitude and (c) direction (radially inward or outward) of the coin's acceleration, and the (d) magnitude and (e) direction (inward or outward) of the frictional force on the coin? The coin is on the verge of slipping if it is placed at a radius of 10 cm. (f) What is the coefficient of static friction between coin and turntable? (Answered)

4098. A single force acts on a 3.0 kg particle-like object whose position is given by x=3.0t-4.0t^2+1.0t^3, with x in meters and t in seconds. Find the work done on the object by the force from t=0 to t=4.0 s. (Answered)

4129. A 2100 kg truck traveling north at 41 km/h turns east and accelerates to 51 km/h. (a) What is the change in the truck's kinetic energy? What are the (b) magnitude and (c) direction of the change in its momentum? (Answered)

4189. what is conservation of momentum?(Answered)

4215. A 140 kg hoop rolls along a horizontal floor so that the hoop's center of mass has a speed of 0.150 m/s. How much work must be done on the hoop to stop it? (Answered)

4230. how fast would a ball have to be thrown upward to reach a maximum height of 121 ft? [Hint: use the discriminant of the equation 16t^2 - v subzero t +h= 0](Answered)

4254. An archer shoots an arrow horizontally at a target 13 m away. The arrow is aimed directly at the center of the target, but it hits 60 cm lower. What was the initial speed of the arrow? (Neglect air resistance.)(Answered)

4334. carmen pours 75 ml of water into a beaker. nick pours 0.75 L of water into a diffrent beaker who has the greater amount of water? use estimation to explain why your answer makes sense

(Answered)

4454. What is the observed length L of the ship if it is traveling 75% the speed of light? (write it in radical form)

(Answered)

4462. Emily passes a soccer ball 7.1 m directly

across the field to Kara, who then kicks the

ball 13.7 m directly down the field to Luisa.

What is the magnitude of the ball's total

displacement as it travels between Emily and

Luisa?

Answer in units of m

013 (part 2 of 2) 10.0 points

Howmany degrees to the side of straight down

the field is the ball's total displacement?

Answer in units of (Answered)

4481. What does Frequency mean?(Answered)

4483. A large kite of mass 3 kg is flying through the air on a windy day. Currently, the tension from the string on the kite has a magnitude of 7.7 N at an angle of Î¸ = 33.5 degrees. The current acceleration of the kite has a magnitude of a = 7.56 m/s2 at an angle of Ï† = 38.5 degrees. The only forces felt by the kite are its own weight, the tension from the string, and a force from the wind. Find the X and Y component of the force of the wind.

Find the X component and Y component of the force of the wind on the kite(Answered)

4560. Assuming a drivers reaction time of 0.25 s, construct a table showing stopping distances for a car travelling at initial speeds of 36kph, 72kph and 90kph with uniform acceleration of

a) 8 m/s^2 ( in dry concrete)

b) 4 m/s^2 ( in wet concrete)(Answered)

4570. A player kicks a football an angle 23 deg to the horizontal with a speed of 12.5m/s. The receiver runs towards the ball at a constant speed to just intercept the ball at ground level. How fast must he run?(Answered)

4570. A player kicks a football an angle 23 deg to the horizontal with a speed of 12.5m/s. The receiver runs towards the ball at a constant speed to just intercept the ball at ground level. How fast must he run?(Answered)

4575. A driver in a car traveling at a speed of 78 km/h sees a cat 101 m away on the road. How long will it take for the car to accelerate uniformly to a stop in exactly 99 m?

(Answered)

4719. The distance (in ft) of an object from a point is given by s(t)=t^2 where t is seconds

a. By using smaller and smaller intervals around 3, estimate the instantaneous velocity at time t=3

(Answered)

4955. Help me solve this Physics problem. Kinematic Equation.: while cruising along a dark stretch of highway at 18 m/s you see, at the fringes of your headlights, some roadkill on the highway. It takes you 0.6 s to react, then you apply the brakes and come to a stop 3.0s later. Assume the clock starts the instant you see the hazard.

What is the TOTAL DISTANCE you travel? (including the time you are moving from your reaction time, as well as the time you are slowing down)(Answered)

4955. Help me solve this Physics problem. Kinematic Equation.: while cruising along a dark stretch of highway at 18 m/s you see, at the fringes of your headlights, some roadkill on the highway. It takes you 0.6 s to react, then you apply the brakes and come to a stop 3.0s later. Assume the clock starts the instant you see the hazard.

What is the TOTAL DISTANCE you travel? (including the time you are moving from your reaction time, as well as the time you are slowing down)(Answered)

4970. What average power would a 1000kg speedboat need to go from rest to 20.0 m/s in 5 secs assuming the water exerts a constant drag force of magnitude 500N and the acceleration is constant. Find an expression for the instantaneous power in terms of the drag force for the mass, acceleration, and time(Answered)

4997. A 100kg man sits 5m from a 2000kg SUV. what is the force of gravity action on the man from the SUV? B) if the man sits twice as far away, what is the new force? C) if the mass of the man doubles and the masss of the SUV triples, how would the force change?(Answered)

4998. 1.calculate the gravitional force between the sun and sagittarius A*, a supermassive black hole in the center of the Milky Way. It has a mass of 8x10^36kg and is located 2.47x10^20m from our Sun, which has a masss of 2x10^30kg. B) how would the force change if both objects sudddenly doubled in mass?. C) if both objects doubled in mass, how would the distance need to change to keep the force unchanged?

2. Mars has two moons, Phobos( mass of 1.07x10^16kg) and Deimos ( mass of 1.5x10^15kg) which get as close as 1.39x10^7m from each other. what is their force of attraction at this distance?

B) what is their force of attraction at

3.27x10^7m, which is their maximum .

C) how would the force change if Phobos lost half its mass while Deimos doubled in mass?

3. A large boulder feels a force of 1N towards a second boulder that is 2m away and has a mass of 3x10^6kg. what id the mass of the frist boulder?

B) how would the force change if the boulders were 6m aparts instead?

C) how far apart would the boulders need to be feel a force of 16N?(Answered)

5066. A plane travels 500 m while accelerating uniformly from rest at the rate of 5.0 m/s. What is the final velocity?(Answered)

5552. Four identical resistors are connected to a battery as shown. When the switch is open, the current through the battery is Io. When the switch is closed, will the current through the battery increase, decrease or stay the same?

(Answered)

5619. The working substance for a Carnot Cycle is 8 lb of air. The volume at the beginning of isothermal expansion is 9 cu ft and the pressure is 300 psia. The ratio of expansion during the addition is 2 and the temperature of the cold body is 90°F. Find (a) Qa, (b) Qr, (c) V3, (d) p3, (e) V4, (f)p4, (g)pm, (h) the ratio of expansion during the isentropic process, and (i) the overall ratio of compression.(Answered)