= 40 N. Q = 60 O m s,k

Transcription

1 Sample Exam #2 Technical Physics Multiple Choice ( 6 Points Each ): F app = 40 N 20 kg Q = 60 O = 0 1. A 20 kg box is pulled along a frictionless floor with an applied force of 40 N. The applied force makes an angle of 60 degrees with the horizontal. If the box starts from rest, what is the acceleration of the box and how fast is it moving after thirty seconds? a. The acceleration is 3 m/s 2 and the velocity is 40 m/s. b. The acceleration is 1 m/s 2 and the velocity is 30 m/s. c. The acceleration is 2 m/s 2 and the velocity is 40 m/s. d. The acceleration is 1 m/s 2 and the velocity is 60 m/s. 40 kg v O = 30 m/s = A box with a mass of 40 kg moves along with a speed of 30 m/s when it encounters a rough section of the floor where there is a 0.20 coefficient of friction. The box slows and comes to a stop. What is the distance the box slides after it encounters the friction until it comes to rest? a m b m c m d. 0.0 m 3. An example of the action-reaction pair of forces described by Newton's third law are: a. the normal force and the weight of a book sitting on the table. b. the frictional force and applied force exerted on a box dragged across a floor. c. the gravitational force of mass A on mass B and the gravitational force of mass B on mass A. d. the frictional force and normal force on a box dragged across a floor.

2 4. A 60 kg jumps out of an airplane with a parachute. He decides not to pull the rip cord until he reaches terminal velocity. If the drag force is equal to F D = bv and b=2kg/ s, what is the magnitude of the velocity when he decides to pull the cord? a m/s b m/s c m/s d. 9.8 m/s m=60 kg h = 6m 60 O 5. A 60 kg box starts from rest and slides down a frictionless ramp with an incline of 60 degrees. What is the acceleration of the box down the ramp? a m/s 2 b m/s 2 c m/s 2 d m/s 2 6. A 30 kg ball is dropped from rest from a height of 40 meters. What is the maximum velocity reached by the ball before it hits the ground? a. +28 m/s b. -28 m/s c. +20 m/s d. -20 m/s

3 20 kg 10 kg 7. A 20 kg block sits on a frictionless table. A string is attached which hangs over a frictionless pulley. A 10 kg block hangs over the end. What is the magnitude of the acceleration of the 20 kg mass? a. 4.9 m/s 2 b. 9.8 m/s 2 c. 20 m/s 2 d. 15 m/s 2 r = 50 m m = A 1000 kg car rounds a 50 meter radius curve at a constant speed. The coefficient of friction of the road is 0.3. What is the force which lets the car maintain its speed as it negotiates the curve? a. gravitational force b. normal force c. frictional force d. weight

4 9. A 1000 kg car rounds a 50 meter radius curve at a constant speed. The coefficient of friction of the road is 0.3. What is the magnitude of maximum velocity which the car can safely negotiate the curve? a m/s b m/s c. 9.8 m/s d m/s 30 kg 60 kg 10. Atwood's machine consists of a frictionless pulley and two masses connected by a cable over the pulley. What is the magnitude of the acceleration of the masses? a m/s 2 b m/s 2 c m/s 2 d m/s 2

5 20 kg Problem One ( 20 Points ): 10 m 60 O = 0.1 Not drawn to scale. A = 0.3 B A 20 kg block starts from rest at the top of a 60 degree incline and slides down the incline. There is a 0.1 coefficient of friction on the ramp. The block then continues to slide along the horizontal surface where there is a 0.3 coefficient of friction. The block then slows, due to friction, until it comes to rest at point B. a. (2) What is the magnitude of the force due to gravity (i.e. the weight ) of the block on the incline? b. (2) What is the magnitude of the Normal Force on the block on the incline? c. (2) What is the magnitude of the frictional force on the block on the incline? d. (2) What is the magnitude of the acceleration of the block down the incline? e. (3) What is the velocity of the block at Point A? f. (3) What is the magnitude of the force of friction on the block on the horizontal? g. (3) What is the acceleration of the block along the horizontal? h. (3) What is the distance between Point A and Point B?

6 Problem Two ( 20 Points ): What is the acceleration and direction of the acceleration of the 40 kg mass?