A.P. Physic's Questions?

Question

1. An elevator has a mass of 1400kg. What is the tension in the supporting cable when the elevator traveling down at 10m/s is brought to test in a distance of 40m. (Assume a constant acceleration.)

2. A jet airplane accelerates on the runway at 3.0. It has two engines which exert a total thrust of 3.0 x 10 ^ 5 N. What is the mass of this airplane?

3. Many people are familiar with the face that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowerder explosion creates hot gases which expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. What is the acceleration of the bullet relative to the recoil of the gun?

Answer 1

1. brought to ... rest by cables I suppose.

Work to stop teh eleveator W = Kinetic Energy Ke

W=Ke

Fh= 0.5 mV^2
F= 0.5 mV^2/h

2. ...at 3.0 I'll asume 3.0 m/s^2

F=ma
m=F/a= 3.0 E+ 5 / 3.0 = 1E+5 kg

3. F1=F2
m1a1=m2a2
a1= (m2/m1)a2