1. What force is needed to accelerate a sled (total mass = 55 kg ) at 1.8 m/s2m/s2 on horizontal frictionless ice? two significant figures and unit

2. Calculate the magnitude of the force on a 88-kg person accelerating at this rate.

3. How much tension must a cable withstand if it is used to accelerate a 1100-kg car vertically upward at 0.80 m/s2m/s2 ?

4. A woman stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.70 of her regular weight.

a) Calculate the magnitude of the acceleration of the elevator.

b) Find the direction of the acceleration.

5. The cable supporting a 2225 kg elevator has a maximum strength of 24680 N .

a) What maximum upward acceleration can it give the elevator without breaking?

7. a)If the coefficient of kinetic friction between a 22 kg crate and the floor is 0.30, what horizontal force is required to move the crate at a steady speed across the floor?

b)What horizontal force is required if k is zero?

8. A force of 39.0 N is required to start a 5.0-kg box moving across a horizontal concrete floor.

a) What is the coefficient of static friction between the box and the floor?

b) If the 39.0-N force continues, the box accelerates at 0.40 m/s^2. What is the coefficient of kinetic friction?

9. The coefficient of static friction between hard rubber and normal street pavement is about 0.70.

a) On how steep a hill (maximum angle) can you leave a car parked?

12. A skier moves down a 16 slope at constant speed.

a) What can you say about the coefficient of friction, k? Assume the speed is low enough that air resistance can be ignored.