1. Express your weight in newtons. From this determine your mass in kilograms.

2. Suppose an airline allows a maximum of 30 kg for each suitcase a passenger brings along. (a) What is the weight in newtons of a 30-kg suitcase? (b) What is the weight in pounds?

3. The mass of a subway car and passengers is 40,000 kg. If its acceleration as it leaves a station is 0.9 m/s2, what is the net force acting on it?

4. As a 2-kg ball rolls down a ramp, the net force on it is 10 N. What is the acceleration?

5. The engines in a supertanker carrying crude oil produce a net force of 20,000,000 N on the ship. If the resulting acceleration is 0.1 m/s2, what is the ship's mass?

6. A person stands on a scale inside an elevator at rest . The scale reads 800 N. (a) What is the person's mass?

(b) The elevator accelerates upward momentarily at the rate

of 2 m/s2. What does the scale read then?

(c) The elevator then moves with a steady speed of 5 m/s.

What does the scale read now?

there is no friction between the mass and the horizontal surface.

7. At the end of Section 1.4, we mentioned that the maximum acceleration of a fist during a particular karate blow was measured to be about 3,500 m/s2 just before impact with the concrete block. If the mass of the fist was approximately 0.7 kg, what was the maximum force delivered to the concrete block?

8. As a baseball is being caught, its speed goes from 30 to 0 m/s in about 0.005 s. Its mass is 0.145 kg. (a) What is the baseball's acceleration in m/s2 and in g's? (b) What is the size of the force acting on it?

9. At the end of an amusement park ride, it is desirable to bring

a gondola to a stop without having the acceleration exceed 2 g. If the total mass of the gondola and its occupants is 2,000 kg, what is the maximum allowed braking force?

10. Under certain conditions, the human body can safely withstand an acceleration of 10 g. (a) What net force would have to act on someone with mass

of 50 kg to cause this acceleration? (b) Find the weight of such a person in pounds, then convert

the answer to (a) to pounds.

11. A hang glider and its pilot have a total mass equal to 120 kg. While executing a 3608 turn, the glider moves in a circle with an 8-m radius. The glider's speed is 10 m/s. (a) What is the net force on the hang glider?

(b) What is the acceleration?

12. On a highway curve with radius 50 m, the maximum force of static friction (centripetal force) that can act on a 1,000-kg car going around the curve is 8,000 N. What speed limit should be posted for the curve so that cars can negotiate it safely?

13. As a spacecraft approaches a planet, the rocket engines on it are fired (turned on) to slow it down so it will go into orbit around the planet. The spacecraft's mass is 2,000 kg, and the thrust (force) of the rocket engines is 400 N. If its speed must be decreased by 1,000 m/s, how long must the engines be fired? (Ignore the change in the mass as the fuel is burned.)

14. A hand exerciser utilizes a coiled spring. A force of 89.0 N is required to compress the spring by 0.0191 m. Find the force needed to compress the spring by 0.0508 m. What is the value of the spring constant for this unit?