Physics

• How many significant figures are there in each of the following? (a) 7.5 0.2 3.690 0.004 (c) 2.8 109 (d) 0.024

2,4,2,2

Using your calculator, find, in scientific notation with appropriate rounding, the value of each of the following. (a) (2.69 104) (6.281 109) / (5.37 104) (b) (3.1416 102) (2.355 105) / (1.082 109)

3.14e+09 0.06838

Carry out the following arithmetic operations. (Enter your answer to the correct number of significant figures.) (a) the sum of the measured values 944, 36.7, 0.97, and 8.5 (b) the product 2.9 2.323 (c) the product 6.33 π

9.90e+02 6.7 19.9

Two boats start together and race across a 52 km wide lake and back. Boat A goes across at 52 km/h and returns at 52 km/h. Boat B goes across at 26 km/h, and its crew, realizing how far behind it is getting, returns at 78 km/h. Turnaround times are negligible, and the boat that completes the round-trip first wins. (a) Which boat wins? (Or is it a tie?)

Boat A, 52, 0

A soccer player kicks a rock horizontally off a 40.0 m high cliffinto a pool of water. If the player hears the sound of the splash2.98 s later, what was the initialspeed given to the rock? Assume the speed of sound in air to be 343m/s.

I got the answer is 3.39 m/s Yf = Yi + Vit + .5at^2 0 = 40 + (0)t + .5(-9.8)t^2 t = 2.857 2.98 - 2.86 = .12 .12 * 343 = 41.16 41.16 = √(x^2 + 40^2) x = 9.70 Vxi = (9.70)/(2.86) Vxi = 3.39

A 5.9 g bullet leaves the muzzle of arifle with a speed of 340 m/s. Whatforce (assumed constant) is exerted on the bullet while it istraveling down the 0.85 m long barrelof the rifle?

U need to find acceleration: use: delta x = 1/2 (v initial + v final)t .85 m = 1/2 (340) t .85 m = 170 t 0.005sec = t Then to find the acceleration v=v initial + at 340 = a(.005) 68000m/s^2 = a Fnet = ma = (.0059kg)(68000m/s^2) = 401.2N Please Rate it.............Thanks

The speed of light is now defined to be 2.997 924 58 108 m/s. (a) Express the speed of light to three significant figures. (b) Express the speed of light to five significant figures. Express the speed of light to seven significant figures.

3.00e+08 2.9979e+08 2.997925e+08

football punter accelerates a football from rest to a speed of10 m/s during the time in which histoe is in contact with the ball (about 0.16 s). If the football has a mass of 0.50 kg,what average force does the punter exert on the ball? 1

A Foot ball accelerates rest from to speed is v = 10 m/s Initial speed is 0 m/s total time is 0.16 s Acceleration a = Δv / Δt = 10 m/s - 0 m/s / 0.16s - 0s = 62.5 m/s2 According toNewtons second law F = ma = 0.50 kg * 62.5 m/s2 = 31.25 N

After falling from rest from a height of 29 m, a 0.54 kg ball rebounds upward, reaching a height of 19 m.? If the contact between ball and ground lasted 2.4 ms, what average force was exerted on the ball?

V1 = √(2gy1) = -23.84 m/s V2 = √(2gy2) = 19.30 m/s dP = m*dV = m*(V2 - V1) = 23.30 kg∙m/s Fav = dP/t = 23.30/.0024 = 9708 N up Source(s): Conservation of momentum Eqs of constant acceleration with time eliminated

(a) Suppose that the displacement of an object is related to time according to the expression x = Bt2. What are the dimensions of B?

dimensions of B = dimension of x/(dimension of t)2 = L/T2 or LT-2

A river has a steady speed of vs. A student swims upstream a distance d and back to the starting point. (a) If the student can swim at a speed of v in still water, how much time tup does it take the student to swim upstream a distance d? Express the answer in terms of d, v, and vs. tup = (b) Using the same variables, how much time tdown does it takes to swim back downstream to the starting point? tdown = (c) Sum the answers found in parts (a) and (b) and show that the time ta required for the whole trip can be written as ta = 2d/v 1 - vs2/v2 . (Do this on paper. Your instructor may ask you to turn in this work.) (d) How much time tb does the trip take in still water? (Use the following as necessary: d and v.) tb = (e) Which is larger, ta or tb? ta tb Is it always larger? Yes No

SOLUTION: River has a steady speed of ,vs Width of the river,d Student can swim at a speed of, v (a) In order to swim up stream, the student must swim against the river's current. so relative speedof the student must be , v-vs thus, requireed time is, tup= d/v-vs _________________________________________________________________ _________________________________________________________________ (b) In order to swim downstream, the student must swim in the river's current direction. so relative speedof the student must be , v+vs thus, requireed time is, tup= d/v+vs _________________________________________________________________ _________________________________________________________________ (c) time required for total trip ta=(d/v-vs) +(d/v+vs) =2dv/v2-vs2 ____________________________________________________ ____________________________________________________ (d) the trip in still water takes, tb=2d/v ___________________________________________________ ___________________________________________________ (e) It is clear that, 2d/v >2dv/v2-vs2 Hence, tb>ta No, it happens only in the direction against to ' river flow

The speed of a nerve impulse in the human body is about 100 m/s. If you accidentally stub you toe in the dark, estimate the time it takes the nerve impulse to travel to your brain. (Assume that you are approximately 2.0 m tall and that the nerve impulse travels at uniform speed.)

time= distance/speed= 2/100 =0.02 seconds

b) A displacement is related to time as x = A sin(2πft), where A and f are constants. Find the dimensions of A. [Hint: A trigonometric function appearing in an equation must be dimensionless.]

"x" is again "displacement", so replace it with "L": L = A sin(2πft). They tell you that "sin(2πft)" is dimensionless. You can throw out any dimensionless number that multiples another number. So throw it out: L = A Now it's simple: With what should you replace "A" in order to make the left side equal the right side? (Hint: "L")

A girl delivering newspapers covers her route by traveling 10.00 blocks west 4.00 blocks north and then 2.00 blocks east. What is her resultant displacement? Read more: http://wiki.answers.com/Q/A_girl_delivering_newspapers_covers_her_route_by_traveling_10.00_blocks_west_4.00_blocks_north_and_then_2.00_blocks_east._What_is_her_resultant_displacement#ixzz1u3eDYM00

A girl delivering newspapers covers her route by traveling 10.00 blocks west, 4.00 blocks north, and then 2.00 blocks east Opposite = 4 (related to y axis on 4 blocks north) Adjacent = 8 (related to x axis on 10 b west - 2 blocks east) tan -1 x (4/8) tan theta - 26.6 degrees since you are looking for the hypotenuse, then sin theta = opp/hyp sin 26.6=4/hypotenuse 4/sin(26.6) = 8.9 blocks Read more: http://wiki.answers.com/Q/A_girl_delivering_newspapers_covers_her_route_by_traveling_10.00_blocks_west_4.00_blocks_north_and_then_2.00_blocks_east._What_is_her_resultant_displacement#ixzz1u3eEjhBO

Anonymous asked A brick is thrown upward from the top of a building at an angle of 25° to the horizontal and with an initial speed of 10 m/s. If the brick is in flight for 2.9 s, how tall is the building?

Answered by Anonymous 29 minutes later Rating:4 Stars Given that angle ? = 25o initial speed uo = 10 m/s time of fight t = 2.90 s --------------------------------------------------- Let x = height of the building When the brick hits the ground its displacement is - x. Hence, - x = ut) + (1/2)(g)(t^2) - x = uo(sin 25)(2.90) + (1/2)(-9.8)(t^2) - x = (10)(sin 25)(2.90) - 4.9(2.90)^2 x = 28.953 m So the height of building is = 28.953m

A person travels by car from one city to another with different constant speeds between pairs of cities. She drives for 30.0 min at 80.0 km/h, 12.0 min at 100 km/h, and 45.0 min at 40.0 km/h and spends 15.0 min eating lunch and buying gas. (a) Determine the average speed for the trip. (b) Determine the distance between the initial and final cities along the route.

Average speed = total distance / total time. distance = speed* time d1 = 80km /h * 30 min. = 80 * 30 /60 = 40 km d2 = 100 *12 / 60 = 20 km d3 = 40 *45 /60 = 30 km ( time is divided by 60 to convert into hour) total distance d = 40+ 20 +30 = 90 km total time = time of traveling + time at rest = (30 + 12 + 45) +15 t = 102min. = 102 /60 = 1.70 hr. s = d /t = 90 /1.70 = 52.94 km/h a) Average speed = 52.94 km /h b) total distance = 90 km

An athlete swims a length L of a pool in a time t1 and makes the return trip to the starting position in a time t2. If she is swimming initially in the positive x-direction, determine the average velocity symbolically in the first half of the swim.

Average velocity = displacement/time Velocity is vector and speed is scalar Taking +x axis as +ve direction, while -xe axis as -ve direction a) In ther first half , average velocity= L/t1 m/s b)In the second half, average velocity = -L/t2 m/s c) In the round trip, average velocity = 0/(t1+t2)=0m/s ( as the displacement is 0) d) Average speed = total distance/total time= ( L+L)/(t1 +t2)= 2L/(t1 +t2) m/s

Projectile motion: In a local bar, a customer slides an empty beer mug down the counter for a refill.? The bartender is momentarily distracted and does not see the mug, which slides off the counter and strikes the floor at distance d from the base of the counter. The height of the counter is h. (a) With what speed did the mug leave the counter? (b) What was the direction of the mug's velocity just before it hit the floor? ? radians below horizontal i suck at these problems, i can never think of the variables as jus being a constant...and the program where i have to submit the answer always says syntax is wrong? i need to see if my answer is wrong or im just inputting it incorrectly..

Best Answer - Chosen by Voters h = 0.5 g t^2 t = sqrt (2h / g) The speed of the mug when it left the counter Vx = d / sqrt (2h / g) The vertical component of this velocity is: Vy = g sqrt (2h / g) = sqrt (2 g h) The angle will be given by: InverseTan (Vy / Vx)

The helicopter view in the figure below shows two people pulling ona stubborn mule. Assume that F1 is 120 N, and F2 is 80 N. The forces are measured in units of newtons(N). This Picture is not showing up but Force 1 isat an angle of 60.0 and force 2 is at 75 (a) Find the single force that is equivalent tothe two forces shown. (b) Find the force that a third person would have to exert on the mule to make the net force equal to zero

Give your information F1=120cos60i+120sin60j and F2=80cos75i+80sin75j R=F1+F2 R11=(120cos60+80cos75)i+(120sin60+80sin75)j=30.706i+181.197j (a)Magnitude R1=183.78 θ=tan-1(181.97/30.706)=80.38 above the +xaxis (b)To have net force you would exert the same magnitude offorce but in the opposite direction. So R2=183.78 θ=180+80.38=260.68 Report Abuse

car is parked on a cliff overlooking the ocean ........? A car is parked on a cliff overlooking the ocean on an incline that makes an angle of 15.0° below the horizontal. The negligent driver leaves the car in neutral, and the emergency brakes are defective. The car rolls from rest down the incline with a constant acceleration of 2.43 m/s2 for a distance of 45.0 m to the edge of the cliff, which is 40.0 m above the ocean. Find the car's position relative to the base of the cliff when the car lands in the ocean. Find the length of time the car is in the air.

Here is how you shoul approach this problem. Normally you are supposed to find accleration of the car as a = g sin(α), but they already gave you the value of a: a = 2.43 m/s² Use fomula for speed of accelerated motion speed = √(2ad), where d is distance travelled by the car down the slope: d = 45m. Now you need horizontal and vertical components of velocity: Vx = speed * cos(α) Vy = speed * sin(α) Write equation of motion of car in free fall: y = 40m - Vy t - gt²/2 Equate y to zero, find t. Now you can find the distance from the cliff x: x = Vx t

A Chinook salmon has a maximum underwater speed of 3.0 m/s,and can jump out of the water vertically with a speed of6.9 m/s. A record salmon has a lengthof 1.5 m and a mass of 63 kg. Whenswimming upward at constant speed, and neglecting buoyancy, thefish experiences three forces: an upward force F exertedby the tail fin, the downward drag force of the water, and thedownward force of gravity. As the fish leaves the surface of thewater, however, it experiences a net upward force causing it toaccelerate from 3.0 m/s to 6.9 m/s.Assuming the drag force disappears as soon as the head of the fishbreaks the surface and that F is exerted until two-thirdsof the fish's length has left the water, determine the magnitude ofF. answer in N

Sincethe salmon is 1.5 m long, 2/3 of its length is 1 m. This is thedistance travelled during the acceleration from 3 m/s to 6.9m/s. The kinetic energy E of a body of mass m moving at velocity vis E = 1/2 * m * v^2 So the work W necessary to make the difference in kinetic energy ofa salmon at 3 m/s and 6.9 m/s is W = 1/2 * 64 kg * (6.9 m/s)^2 - 1/2 * 69 kg * (3 m/s)^2= 1235.52 J Now work is force times distance W = F * d which you can solve for F F = W / d and inserting the distance (2/3 of the salmons length, seeabove): F = 1235.52 J / 1 m = 1235.52 N Nowthis is the net force necessary for the acceleration. This netforce is the sum of the tail fin force Ff and gravity Fg. F = Ff + Fg (the force of gravity acts downwards, so it will assume a negativevalue) Solving this for the tail fin force gives Ff = F - Fg Now gravity on a salmon of mass m = 61 kg is Fg = - g * m = - 9.81 m/s^2 * 64 kg = - 627.2 N So the tail fin force is Ff = 1235.52 N - (- 627.2 N) = 1862.72N

A tortoise can run with a speed of 0.13 m/s, and a hare can run 20 times as fast. In a race, they both start at the same time, but the hare stops to rest for 5.0 minutes. The tortoise wins by a shell (35 cm). (a) How long does the race take?

Speed of Tortoise = 0.13m/s = S Speed of Hare = 20x.13 = 2.6m/s = S' let time taken by tortoise to reach final line = t sec time taken by hare till tortoise wins = t+(5x60) = t-300 [it takes rest for 300 s where distance travelled is 0] Distance travelled by tortoise = 0.13t Distance travelled by hare = 2.6(t-300) Difference between the distances of tortoise and hare is 0.35 m. 0.13t - 2.6(t-300) = 0.35 => t = 315.65 s Distance of the race = Time taken by tortoise x Speed of tortoise = 315.65 x 0.13 = 41.0342 m The race is 41.0342 m long.

A golfer takes two putts to get his ball into the hole once he ison the green. The first putt displaces the ball 7.8 m east, and thesecond 6.89 m south. What displacement would have been needed toget the ball into the hole of the first putt? Answer in units ofm. Whta is the direction (in degrees S of E)? Answer in units ofo

The first putt = 7.8m i the second putt = - 6.89 j the displacement directly to hole R = √ ( 7.8)2 + (6.89)2 =10.4m Direction θ = tan-1( -6.89 / 7.8)= - 41.45 0

A 3.0 kg object hangs at one end of a rope that is attached to a support on a railroad car. When the car accelerates to the right, the rope makes an angle of 4.0 degree with the vertical. Find the acceleration of the car.

The mass is not important in an acceleration problem use: a=gsinθ a=9.8sin4 a=0.684m/ss

A fisherman catches two striped bass. The smaller of the two has a measured length of 95.42 cm (two decimal places, four significant figures), and the larger fish has a measured length of 120.6 cm (one decimal place, four significant figures). What is the total length of fish caught for the day? (Enter your answer to the correct number of digits.)

The smaller one of the two striped bass measurer A length of 95.42cm The larger fish measures 120.6 cm Hence the total length of fish caught for the day will be = 95.42 + 120.6 cm Calculating : total length = 216.02 cm Hence , rounded for 4 significant digits Ans : 216.0 cm

A river flows due east at 1.00 m/s. A boat crosses the river from the south shore to the north shore by maintaining a constant velocity of 15.0 m/s due north relative to the water. (a) What is the velocity of the boat relative to shore? m/s ° (north of east) (b) If the river is 200 m wide, how far downstream has the boat moved by the time it reaches the north shore? m

The velocity of the boat with respect to the ground is Vbg = v[ (Vbw)^2 -(Vwg)^2 ] = v(15m/s)^2 - (1m/s)^2 = 14.966m/s The angle through which the boat drift is ? = sin^-1 (1 m/s /15m/s ) = 3.822o the angle made with boat with the direction of the river is f = 90- 3.822 = 86.17 north of east. b) If the river is 200m the drift in distance is tan 3.822 = x / 200m x = 200 tan 3.822 = 13.36m

A fathom is a unit of length, usually reserved for measuring the depth of water. A fathom is approximately 6ft in length. Take the distance from Earth to the Moon to be 240,000 miles, and use the given approximation to find the distance in fathoms.

We know the conversion between mile and feet is 1 mile = 5280 ft And it is given that 1 fathom = 6ft 1 ft = (1/6)fathom Then the distance between Earth to Moon = 240,000 miles = (240,000 miles)(5280ft/mile) = 1267200000 ft = (1267200000)(1/6)fathom = 211200000fathom

A bag of sugar weighs 3.00 lb on Earth. What would it weigh in newtons on the Moon, where the free-fall acceleration is one-sixth that on Earth? = ? N Repeat for Jupiter, where g is 2.64 times that on Earth. = ? N Find the mass of the bag of sugar in kilograms at each of the three locations. Earth= kg Moon= kg Jupiter= kg

Weight = mass x acceleration Earths acceleration is 9.8 m/s*2 1 kg = 2.2 lbs, so 2.0 lbs x 1 kg/2.2 lbs = 0.91 kg The bag would have a weight of 9.8 x 0.91 = 8.9 N 1. 8.9 x 1/6 = 1.5 N 2. 8.9 x 2.64 = 23.5 N The mass of the bag at all three locations is 0.91 kg. Mass does not change, the different locations only change its weight.

A 76.5-kg skydiver reaches a terminal speed of 58.7 m/s with her parachute undeployed. Suppose the drag force acting on her is proportional to the speed squared, or Fdrag = kv^2. (a) What is the constant of proportionality k? (Assume the gravitational acceleration is 9.8 m/s2.) (b) What was the magnitude of the acceleration when she was falling at half terminal speed? Please help!! Thank You

a) define positive as downward, we have W - Fdrag = ma mg - kv2 = ma at terminal speed, a = 0 so mg = kv2 k = mg/v2 k = (76.5kg)(9.8m/s2)/(58.7m/s)2 k = 0.218 kg/m b) use mg - kv2 = ma a = g - kv2/m a = 9.8m/s2 - (0.218kg/m)(0.5(58.7m/s))2/76.5kg a = 2.45 m/s2

An object of mass m is dropped from the roof of a building of height h. While the object is falling, a wind bl? An object of mass m is dropped from the roof of a building of height h. While the object is falling, a wind blowing parallel to the face of the building exerts a constant force F on the object. (a) How long does it take the object to strike the ground? Express the time t in terms of g and h. (b) Find an expression in terms of m and F for the acceleration ax of the object in the horizontal direction (taken as the positive x-direction). (c) How far is the object displaced horizontally before hitting the ground? Answer in terms of m, F, g, and h. (c) Find the magnitude of the object's acceleration while it is falling, using the variables F, m, and g.

a) t = √[2h/g] b) a(x) = F/m c) Xh = ½*a(x)*t² = ½*(F/m)*2gh = Fgh/m d) a(x) = F/m; a(y) = g; ....a = √(a(x)²+a(y)²) a = √[(F/m)² + g²] 3 years ago Report Abuse

A car starts from rest and travels for t1 seconds with a uniform acceleration a1.? The driver then applies the brakes, causing a uniform acceleration a2. If the brakes are applied for t2 seconds, determine the following. Answers are in terms of the variables a1, a2, t1, and t2. (a) How fast is the car going just before the beginning of the braking period? (b) How far does the car go before the driver begins to brake? (c) Using the answers to parts (a) and (b) as the initial velocity and position for the motion of the car during braking, what total distance does the car travel? Thank you!

a) velocity is given by v(t)=v0+at, here v0=0, a=a1 and t=t1, so we have that v(t)=a1 t1 b) distance traveled = v0t + 1/2 at^2 so here, that means dist = 1/2 a1 t1^2 c) the distance the car travels once the brakes are applied is dist = v0 t + 1/2 at^2 now, v0=a1 t1 and a=-a2 t=t2 so you can write dist in the braking phase = v0 t1 t2 -1/2 a2 t2 ^2 now, the problem does not state whether the car brakes to rest, if it does we can write t2 in terms of t1 v(t)=v0 + at in this phase, if the final velocity at t=t2 is zero, and v0=a1 t1, we have that: 0=a1 t1 - a2 t2 or t2= a1 t1/a2 and you can use this expression in your final answer for part c

A train 400m long is moving on a straight track with a speedof 82.4 km/h. The engineer applies the brakes at a crossing,and later the last car passes the crossing with a speed of 16.4km/h. Assuming constant acceleration, determine how long thetrain blocked the crossing. Disregard the width of thecrossing.

deltax=400m=0.4 km vaverage=x/t 0.5(vi+vf)=delta x/t delta t 2* 0.4/(82.4+16.4) hr * 3600s/hr=29.15 s

A jet airliner moving initially at 300 mi/h due east enters a region where the wind is blowing at 105 mi/h in a direction 36.0 degrees north of east. What is the new velocity of the aircraft relative to the ground?

let's make x axis pointing east, y axis pointing north Vx = 300 + 105 cos36 = 384.95 Vy = 105 sin36 = 61.72 V = sqrt(Vx2 + Vy2 ) = 390 mi/h θ = tan-1 (Vy/Vx) = tan-1(61.72/384.95) = 9.1 degree new velocity is 390 mi/h in a direction 9.1 degrees north of east

The force exerted by the wind on the sails of a sailboat is 500 N north...? The force exerted by the wind on the sails of a sailboat is 500 N north. The water exerts a force of 240 N east. If the boat (including its crew) has a mass of 270 kg, what are the magnitude and direction of its acceleration?

magnitude: The two forces are at right angles so Pythagorean theorem can be applied. F^2 = 500^2 + 240^2 F = 554N F = ma 554 = 270a a = 2.05 m/s^2 Direction: It goes north east a bit. tan alpha = 500/270 alpha = 61 degrees 3 years ago Report Abuse

Car traveling east at 33.1 m/s passes a trooper hiding at the roadside...? A car traveling east at 33.1 m/s passes a trooper hiding at the roadside. The driver uniformly reduces his speed to 25.0 m/s in 3.20 s. (a) What is the magnitude and direction of the car's acceleration as it slows down? magnitude ____m/s2 (b) How far does the car travel in the 3.20-s time period? _______meters Thanks for the help

qa v = u + at 25 = 33.1 + 3.2a 3.2a = - 8.1 a = - 8.1/3.2 = - 2.53 m/s^2 [ the minus sign indicates direction opposite to that of motion] --------------------- qb distance travelled = average velocity*time = 0.5(33.1 + 25)*3.2 = 92.96 m

Anonymous asked A train is traveling down a straight track at 20 m/s when the engineer applies the brakes, resulting in a uniform acceleration of 1 m/s2. how far will the train move in a 40s time interval, starting at the instant the brakes are applied? I need the steps broken down if that is at all possible

since the brakes were applied, it would be a uniform accelerationof -1 m/s2, right? so the first thing is that the train won't be moving for the full40 seconds. the brakes will stop the train after only 20seconds v=v0+at 0=20-1.t t=20s x=1/2 at^2+v0t 0.5*-1*20^2+(20)(20) x=200m