**Problem Set Three**

Notes: **Use 9.8 m/s** **2** **for the acceleration due to gravity**. For Newton’s Law calculations, mass must be expressed in kg and velocity must be expressed in m/s.

1. An automobile weighs 2000 lb. Calculate the weight of the car in N and its mass in kg.

2. What is the acceleration of a car that moves from a speed of 2.5 m/s to a speed of 25 m/s during a time of 6.5 s?

3. An astronaut has a mass of 120 kg. She recedes from her spacecraft using spurts of gas from a small unit on her back. If the force generated by the gas spurt is 50 N, calculate her acceleration.

4. A steady 45 N horizontal force is applied to a 15 kg object on a table. The object slides against a friction force of 30 N. Calculate the acceleration of the object in m/s.

5. A man with a mass of 110 kg slides down a vertical pole with an acceleration of 9 m/s2. What is the frictional force acting on the man?

6. A space ship has a mass of 75,000 kg. What net force is required to accelerate it to 20 m/s2 ?

7. A net force of 3500 N accelerates a car from rest to 46 km/h in 5 s. What is the mass of the car?

8. A force of 3.2 N is applied to an 8.5 gram rifle bullet. What is the bullet’s acceleration?

9. An automobile is pulled by a horizontal tow line, with a force of 950 N. If its acceleration is 1.0 m/s2, calculate the mass of the automobile.

10. What is the weight in Newtons of a 250 gram box of breakfast cereal?