Calculating the reaction force on the ground from a falling ladder.

An 8 m long, 12kg, uniform ladder leans against a frictionless wall making an angle of 65 degrees with the floor. A 75 kg person is able to climb to the 7 m mark on the ladder before it slips. What is the reaction force on the ground?

Half life of a radio active material

A radio active substance has a half life of 30 days. Calculate (a) the radioactive disintegration constant (b) The average life (c) the time taken for ¾ of the original number of atoms to disintegrate and (d) the time taken for 1/8 of the original number of atoms to remain unchanged

Displacement of a beam of Hydrogen ions subjected to magnetic and electric fields.

A uniform electric field of 1.6 x 10^3 V/m and a uniform magnetic field of 3.34 x 10^-3 Wb/m^2 are parallel to each other and are acting along the Z-direction. A beam of Hydrogen ions of energy 150 eV is released in the X direction. A photographic plate is placed normal to the motion of the ions at a distance of 0.5m from the origin. (1) How long after leaving the gun, will the ions hit the plate? (2) Calculate the displacement of the ions in the Y and Z directions.

Calculating the period of revolution and the orbital radius of an electron in a magnetic field.

An electron of energy 10eV is circulating in a plane at right angles to a uniform field of strength 10^-4 Wb/m^2 (1 Gauss). Calculate the radius of the orbit of the electron and its period of revolution.

Equilibrium

What magnitude of force applied horizontally at the axle of the wheel is necessary to raise the wheel over an obstacle of height h? The wheel's radius is r and its mass is m. The wheel is shown on a flat surface resting against a step of height h. The point touching the step is at 4 o'clock on the wheel. I know a picture would be more helpful.