Mechanics | Relativity Answers

A 15.2 kg box is slid along the ground with a coefficient of kinetic friction of 0.569.

a. If the box moves 8.04 m, what is the amount of work done by friction on the box?

b. If the box moves 6.12 m and has an acceleration of 0.972 m/s^2. what is the work done on the box by the applied force?

The motor of a overhead crane raises a load of 810kg at a velocity of 0.4m/s. the efficiency is 80 percent.

What is the output power?

A body of mass 2 kg is moving on a smooth horizontal surface under the action of a horizontal force F=55+t² (N). Calculate the velocity of the body at t=5s, assuming the body was at rest at t=0. (Answer is 158.3m/s)

A particle of mass m0 moving with velocity u in the first frame. The second frame is moving

at velocity v with respect to the first frame, along the x-axis, and the particle has a velocity u

´as seen in the second frame. Showing that momentum and energy are the components of a

4-vector is to write the momentum and energy of a particle in terms of its real mass and

velocity in one Lorentz frame and then use the Lorentz transformation for velocity (that is,

the velocity addition law) to and the form of the momentum and energy of the particle in a

second Lorentz frame.

A positron and an electron at rest in frame S combine and annihilate another, producing two photons. (a) What is the energy and momentum of each photon in this frame? What quantities are conserved in this process? (b) Prove that the positron and electron cannot combine to produce only one photon.

A muon has a lifetime 2×10^-6 in it's rest frame. It is created 100 km above the earth moves towards it at a speed of 2.97 x 10^8 m/s. At what altitude does it decay?

What is g at height h

A ball is thrown at 20 m/s from the roof of a building 25 high at an angle of 30 degrees below the horizontal. At what height above the ground will the ball strike the side of another building 20 meters away from the first

If the normal pushing force of 25 LBS is required to push a wheel chair on a level floor for 160 lbs patient, calculate the pushing force of the wheelchair carrying 160 LBS weight when the ramp angle is 20 degrees.

A man stands on the roof of a 15.0-m-tall building and throws a rock with a velocity of magnitude 30 m/s at an angle of 33° above the horizontal. You can ignore air resistance. Calculate. A) the maximum height above the roof reached by the rock; B) the magnitude of the velocity of the rock just before it strikes the ground; and C) the horizontal range from the base of the building to the point where the rock strikes the ground.