Other Physics Answers

A person wanted to have a warm bath at 40°c and placed 5.0kg of water in a basin at 85°c. What mass of cold water at 25°c must be added to the hot water to obtain the choice of bath. Neglecte heat losses and take specific heat capacity of water as 4200J/ kg/ k

Density is a measure of the mass per unit of volume for a material. Mathematically, this can be expressed in units of kg/m3. Given that the equation for the volume of sphere is based on radius, the density of Earth is ___x10³ kg/m³

Question 2 options:

Given the value for the universal gravitational constant, the average value for the acceleration due to gravity at the surface of Earth, and the radius of Earth, Earth’s mass is ____x10²⁴kg. 

The mass of each lead ball in Cavendish’s experiment was 195 kg. Given the value of G, the magnitude of the expected force of attraction between two of these balls if their centres were separated by 1.0400 m is ___x10^-6 N.

A river flows due south with a

speed of A man steers a motorboat across the river; his

velocity relative to the water is due east. The river is 800 m

wide. (a) What is his velocity (magnitude and direction) relative to

the earth? (b) How much time is required to cross the river?

(c) How far south of his starting point will he reach the opposite

bank?

A damped oscillator makes 100 oscillations per second. The energy decays to 1/e of

its initial value in 10 ms. How many oscillations per second will the oscillator make

in the absence of damping.

What is the radiant emittance of a black body at

a temperature of 400K ?[o is 5.672×108 MKS unit]

Please give answer in watt per meter square

Work, energy, and energy conservation

1. How much work is done on a 2 kg object when it changes its velocity from 20 m/s to 40 m/s?

2. A pile of books of mass 50 kg is placed on top of a cabinet 3 m high. What is the gravitational

potential energy of the pile of books?

3. A box is pulled by a force of 200 N making an angle of 30 degrees with the horizontal. How

much work is done on the box if it is displaced by 20 m?

A 1.0 kg block is pushed 3.0 m at a constant velocity up a vertical wall by a constant force applied at an angle of 28.0 ◦ with the horizontal, as shown in the figure. The acceleration of gravity is 9.81 m/s 2.If the coefficient of kinetic friction between the block and the wall is 0.30, find a) the work done by the force on the block.

a solar collector is thermally insulated so that conduction is negligible in comparison with radiation. On a cold but sunny day the temperature outside is -20°c and the sun irradiates the collector with a power cell unit area of 300W / m^2. Treating the collector as a blackbody (emissivity=1), determine it's interior temperature after the collector has achieved a steady state condition (radiating energy as fast as it is received)