1. A rubber ball weighs 49N. What is the acceleration of the ball if an upward force of 69N is applied? (m = 5.0 kg; = 4.0 m/s2)

2. a) What is the weight of a 20.0-kg stone? b) What force is needed to accelerate the stone upward at 10 m/s2?(a)Fw = mg = 196N; b)Fa = 400 N)

3. A rocket weighs 9800 N. a)What is its mass? b)What applied force will give an acceleration of 4.0 m/s2?(a)m = 1.0 X 103 kg;b)Fa = 14000 N)

4. A small rocket weighs 14.7 N. a)What is its mass? b)The rocket is fired from a high platform but its engine fails to burn properly. The rocket gains a toal upward force of only 10.2 N.What is the acceleration of the rocket?(a)m = 1.5 kg;b)a = - 3.0 m/s2 downward)

5. A force of 91 N is exerted straight up on a stone that has a mass of 0.75 kg. Calculate a)the weight of the stone; b)the net force acting on the stone; c)the acceleration of the stone.(a)Fw = 7.4 N;b)netF = 84 N upward; c)a = 110 m/s2)

6. A rocket that weighs 7840 N on the earth is fired. The force of propulsion is +10,440 N. Determine a)the mass of the rocket; b)the acceleration of the rocket and c)the velocity of the rocket at the end of 8.0 s. (a)m = 8.0 x 102 kg; b)a = 3.3 m/s2, c)vf = 26 m/s)

7. A person weighing 490 N, downward stands on a scale, pushing upward in an elevator. In all cases consider ONLY the person's gravitational force, Fw, and the upward Fscale on the person. Draw free-body sketches and label a and the forces on the person to solve each case: a) What is the scale reading, Fscale, when the elevator is at rest-no acceleration?

b) The scale(ignore the elevator) starts to accelerate the person upward at 2.2 m/s2. What is the new value for Fscale?

c) What is the Fscale reading when the scale(ignore the elevator) rises at a constant velocity-no acceleration?

d) The scale(elevator) begins to negatively accelerate as it nears the proper floor. Does the Fscale reading increase or decrease?

e) The Fscale(elevator) starts accelerating downward. Does the Fscale reading increase or decrease?

f) What is the Fscale reading when the scale descends at a constant velocity-no acceleration?

g) If the cable snapped and the scale(elevator) fell freely, what would Fscale read?

(a)Fscale = 490 N;b)m = 50 kg,Fscale = 600 N; c)Fscale = 490 N; d)Decrease; e)Decrease; f)Fscale = Fw = 490 N; g)Fscale = 0)