Physics Answers

Derive the momentum of inertia component of a rotating rigid body

a student eat a dinner containing 3.0 x 106J of energy. He wishes to do an equivalent amount of work in a near by gym by lifting a 60kg object.How many times

Data required: G = 6.67 x 10-¹¹ N m² kg-²

mass of the Earth = 6.0 x 10^24 kg radius of the Earth = 6.4 x 10^6 m gravitational field strength close to the surface of the Earth is 9.8 N kg-1 15

1.) What is the gravitational potential energy of a 60 kg student on the surface of the Earth? What then, is the minimum energy that would be required to get this student completely out of the Earth’s gravitational field?

2.) You’re in the design of mission carrying humans to the surface of the planet Mars, which has a radius of 3.38 x 106 m and a mass of 6.24 x 1023 kg. The Earth weigh of the Mar’s lander is 39,200 N. Calculate its weight and the acceleration due to Mar’s gravity at 6.0 x 106 m above the surface of Mars.

(Show the solution if it's possible, thanks)

1. A flywheel, in the form of uniform disk, is 4.0 m in diameter and weighs 637 N. What will be its angular acceleration if it is activated upon by net torque of 225J?

2. When you switch your room fan from medium to high speed, the blades accelerate at 1.2 radians per second squared for 1.5 seconds. If the initial angular speed of the fan blades is 3.0 radians per second, what is the final angular speed of the fan blades in radians per second?

(Show the solution if it's ok with you, thank you)

 A uniform electric field exists in the region between two oppositely charged plane parallel plates. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate, 1.60 cm distant from the first, in a time interval of 3.20 x 10-6 s. 

(a) Find the magnitude of the electric field.

 (b) Find the speed of the proton when it strikes the negatively charged plate.

What physical factors are important for an athlete doing a long jump? What about the high jump?

A 50-g ice cube at -4

oC is dropped into an insulated container conatining 200mL at 25°CWhen thermal equilibrium is reached, the temperature of water dropped to 9°C. How much heat

is gained by the ice cube ?

A 1-kg metal sample is heated to 90

oC and then dropped into an insulated

container containing 200mL of water at 25

oC. When thermal equilibrium is reached, the

temperature of water rose to 40

oC.

1. What is the final temperature of the metal sample ?

2. What happened after the metal sample is dropped into the beaker?

3. Calculate the Q of the metal sample.

4. Calculate the specific heat capacity of the metal sample.

Lesson: 2nd Law of Thermodynamics and Entropy

1. If you know that the change in entropy of a system where heat was added is 40 J/K, and that the temperature of the system is 200 K, what is the amount of heat added to the system?

2. If I add 30J of heat to a system so that the final temperature of the system is 26.85 °C, what is the change in entropy of the system?

3. Suppose 0.2 kg of ice at 0°C is in 0.5 kg water at 30°C. Determine the change in entropy of the ice as it melts at 0°C.

The density of air at standard conditions (p = 1 atm and t = 20°c) is 1.28 kg/m³. At what pressure is the density 0.64 kg/m³ if the temperature and number of molecules are kept constant?