Physics Heat & Thermodynamics Level: High School
At what rate does the same person’s head absorb the sun’s energy if it is bald with e = 0.205 under the same conditions .5.12 J/s
Physics Heat & Thermodynamics Level: High School
At approximately what rate does the top of a person’s head absorb the sun’s energy on a clear day if it is covered with hair (e = 0.760) , has a surface area of 227 square centimeters (assumed flat), and the person stands straight with the Sun making an angle of theta = 37.5 degree with vertical .
Physics Heat & Thermodynamics Level: High School
A 31.8 g glass thermometer reads 22.0 degreeC it is placed in 121 mL of water . When the water and the thermometer come to equilibrium , the thermometer reads 39.9 degreeC . What was the original temperature of the water (in Celsius) ?
Physics Heat & Thermodynamics Level: High School
A small immersion heater is rated at 355 W . Estimate how long it will take to heat a cup of soup (assume this is 290 mL of water) from 21.0 degreeC to 48.4 degree C?
Physics Rotational Mechanics Level: High School
A homogeneous spherical star (before and after) of mass M = 3.2 x 10^31 kg and radius of Rsub 1 = 6.00 x 10 x 10 meters collapses to the size of a white dwarf with radius Rsubf = 5.00 x 10^7 meters . (Notice the notation for subscripts , e.g. , omega subf = letter Greek letter ‘omega’ with a sub f notation )a. Calculate the moment of inertia for an axis through the center of mass before collapse .
b. Calculate the initial angular momentum of the star, if the original angular velocity is omega sub I = 1.05 x 10^-6 rad/sec .
c. Calculate the rotational kinetic energy of the original star ?
d. What is the final angular velocity , omega sub f, of the white dwart ?
Physics Force & Laws Of Motion Level: High School
A cylinder shell has a radius , r , a and a mass , m . It is released from rest and moves down the inclined plane .a. Assume first that the plane is frictionless and that the cylinder shell slides down the plane . Calculate the speed of the shell at the bottom of the plane .
b. Now assume that the plane causes the shell to roll without slipping from its initial position . Again calculate its speed at the bottom of the plane . Again assume the shell starts form rest .
c. Explain in less than 50 words the physical reasons for any difference between the answers to Part (a) and (b).
Physics Force & Laws Of Motion Level: High School
A subway train consists of three cars, each having a mass of 15000 kg . The first car , acting as the engine, pulls ahead with a traction force of 42000 Newtons . Friction exerts a backwards drag of 900 Newtons on each car .a. What is the acceleration of the train.
b. What is the tension Tsub 1 in the coupling between car 1 and car 2 ?
c. If the train started at rest, what is the speed at t = 10 sec ?
d. If the train started at position x = 0 , what is the position at t = 10 sec ?
Physics Heat & Thermodynamics Level: High School
Explain in less than 50-words why there is a minimum temperature (absolute zero) but no maximum temperature ?Physics Gravitation Level: High School
Would a flash float to the surface , sink or stay at the same depth , if the gravitational field of the Earth increased ?Physics Gravitation Level: High School
If our Sun shrank in size to become a black hole, use the Newton’s Universal Gravitational Law to explain how the Earth’s orbit would be affected ?
Physics Rotational Mechanics Level: High School
A friend says that a baby cannot rotate when the net torque acting on it is zero . Your friends assertion is incorrect . Correct it in less than 50-words .Physics Work,Power & Energy Level: High School
(a) Does the string that supports a pendulum bob do work on the bob as it swings to and fro ?(b) Does the force of gravity do any work on the bob ?
Physics Force & Laws Of Motion Level: High School
A lunar vehicle is tested on Earth at a speed of 10 km/h . When it travels as fast on the Moon , is it momentum more , less , or the same ?Physics Force & Laws Of Motion Level: High School
Which teams wins in tug-of-war, the team that pulls harder on the rope , or the team that pushes harder against the ground ?Physics Force & Laws Of Motion Level: High School
Does a baseball bat slow down when it hits a ball ?a. Yes, a baseball exerts an external force on the bat; thus decelerating the bat.
b. No, the more massive bat is physically unimpeded by the baseball.
c. Yes, a baseball and bat interaction is best described by Newton’s Universal Gravitational Law.
d. No, the mass differential is more driven by the acceleration of the two.
e. Yes, but it is directly proportional to the location of the centers of mass of the two objects.