Four questions that i dont know how to do at all. 1. A student standing on a scale in an elevator at rest sees that it reads 650 N. As the elevator rises, the scale reads 700 N. Find the acceleration of the elevator. 2. A sign in an elevator states that the maximum occupancy is 20 persons. Suppose safety engineers assume the mass of an average person is 70 kg. The elevator itself has a mass of 540 kg. The supporting cable can tolerate a maximum force of 32471 N. What is the greatest acceleration the elevator's motor can produce without snapping the cable? 3. A student pushes a 12.9 kg lawnmower. The handle makes a 28 degree angle with the ground. If the friction is 68 N, find how much force the student must apply to the lawnmower in order to accelerate it at 3.7 m/s^2. 4. A 30 kg box is pushed across the level ground with a horizontal force of 172 N. As a result it accelerates at 5 m/s^2. How much friction must be present? please explain every step because im totaly lost and my teacher just threw us right into it without explain at all. Very much apperciated.