CAN SOMEONE HELP EXPLAIN AND DERIVE THIS FOR ME ? BECAUSE I KNOW THE ANSWER IS 24J BUT HOW ??
In: Physics
How long does it take light to reach us from the Sun, 1.50 ×108km away IN MINUTES?
In: Physics
Find the pressure difference on an airplane wing if air flows over the upper surface with a speed of 115 m/s. If the area of the wing is 32m^2, what is the upward force exerted on the wing?
No idea how to approach this as we dont have the air speed below
the wing.
In: Physics
The naturally occurring isotope K40 is widely spread in the environment.
Infact, the average concentration of potassium in the crustal rocks is 27 [g/kg] and in the oceans is 380 [mg/liter].
K40 occurs in plants and animals, has a half-life of 1.3 billion years and an abundance of 0.0119 percent.
Potassium's concentration in humans is 1.7 [g/kg].
In urine, potassium's concentration is 1.5 [g/liter].
1) Calculate the specific activity of K40 in Becquerels per gram and in Curies/gm of K40.
2) Calculate the specific activity of K40 in Becquerels per gram and in Curies per gm of overall potassium.
3) Calculate the specific activity of K40 in urine in [Bq/liter].
In: Physics
A cart loaded with bricks has a total mass of 10.1 kg and is pulled at constant speed by a rope. The rope is inclined at 29.9 ◦ above the horizontal and the cart moves 8 m on a horizontal floor. The coefficient of kinetic friction between ground and cart is 0.7 .
The acceleration of gravity is 9.8 m/s2 .
1. What is the normal force exerted on the cart by the floor?
Answer in units of N.
2. How much work is done on the cart by the rope?
Answer in units of kJ.
3. Note: The energy change due to friction is a loss of energy.
What is the energy change Wf due to fric- tion?
Answer in units of kJ.
In: Physics
Two positive charges of 1.1e-10 C are placed on the x axis at distances +30 cm and -30 cm from the origin, respectively. A third positive charge of 2e-11 C can be moved along the y axis. At what value of y is the electrostatic force on the third charge is maximal?
In: Physics
In a shuttle craft of mass m = 2100 kg, Captain Janeway orbits a planet of mass M = 5.98
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A hollow sphere of radius 0.150 m, with rotational inertia I = 0.0460 kg·m2 about a line through its center of mass, rolls without slipping up a surface inclined at 23.2° to the horizontal. At a certain initial position, the sphere's total kinetic energy is 44.0 J. (a) How much of this initial kinetic energy is rotational? (b) What is the speed of the center of mass of the sphere at the initial position? When the sphere has moved 1.10 m up the incline from its initial position, what are (c) its total kinetic energy and (d) the speed of its center of mass?
In: Physics
In: Physics
Suppose that a bicyclist is traveling at an energetic 20 mph on a flat road, and the combination of rolling resistance and air drag is 10 pounds. (48 pts, 8 pts each part) a. What is the rate at which the bicyclist is doing useful work at this speed, in watts and horsepower? b. Measurements indicate that this performance requires conversion of food energy at a rate of 8 kcal/min. What is the first-law efficiency of the cyclist as a machine in converting energy to work at 20 mph? Assume that in a sedentary state, the rate of energy consumed by the cyclist’s body is 1.5 kcal/min. c. What is the bicyclist’s “miles per gallon” equivalent if the energy in the extra food consumed to power the bicycle is equated to the energy in gasoline? d. If the needed energy is obtained from energy bars containing 200 Calories and costing $1.50 each, what is the bicyclist’s fuel cost in cents per mile? What is the fuel cost in cents per mile for a car that gets 20 mpg using $3 per gallon gasoline? e. What are the CO2 emissions per mile for the bicyclist and the car? Consider only what is being emitted as they proceed. Do not include lifecycle considerations, and for the bicyclist only include the CO2 associated with propulsion. For the bicyclist, assume the energy bar consists of carbohydrates with a simplified molecular formula of CH2O and an energy content of 4 kcal/g. For the car, assume the gasoline consists of entirely of iso-octane, C8H18, with a specific gravity of 0.7 and an energy content of 45 MJ/kg. f. Without doing a calculation, name at least three elements of a lifecycle CO2 analysis that would change the emissions per mile calculation above, and whether they would tend to increase or decrease the value for each of the transportation modes.
In: Physics
A spherical marble that has a mass of 45.0 g and a radius of 0.500 cm rolls without slipping down a loop-the-loop track that has a radius of 30.0 cm. The marble starts from rest and just barely clears the loop to emerge on the other side of the track.
1)
What is the minimum height that the marble must start from to make it around the loop? (Express your answer to three significant figures and in cm.)
In: Physics
A geosynchronous satellite is one that stays above the same point on the equator of the earth. Determine the height above the Earth's surface such a satellite must orbit and find it's speed. (Note that the radius in equation is measured from the center of the earth, not the surface.) You may use the following constants:
The universal gravitational constant G is 6.67 x 10-11 N m2 / kg2 .
The mass of the earth is 5.98 x 1024 kg.
The radius of the earth is 6.38 x 106 m.
Hint: In order for the satellite to remain in orbit, the gravitational force must equal the centripetal force:
In: Physics
1.) A 5.99?C and a -2.04?C charge are placed 16.2cm apart.
Where can a third charge be placed so that it experiences no net force? [Hint: Assume that the negative charge is 16.2cm to the right of the positive charge.
2.) A downward force of 3.0 N is exerted on a -8.4?C
charge.
a.) What is the magnitude of the electric field at this point?
b.)What
is the direction of the electric field at this
point?
In: Physics
A thin uniform pole of length 30 m is pivoted at the bottom end. Calculate the most probable point of rupture on the pole as the pole falls.
In: Physics
In: Physics