Physics

If an object is moving eastward and slowing down, then the direction of its acceleration vector is ____.

. westward7.

Acceleration

Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.

23. Ten seconds after being dropped from rest, a free-falling object will be moving with a speed of ____. a. about 10 m/s. b. about 50 m/s. c. about 100 m/s. d. more than 100 m/

Answer: C Since the speed of a free-falling object increases by 10 m/s every second, the speed after ten of these seconds will be 100 m/s. You could use the kinematic equation vf= vi+ a*t where vi=0 m/s and a = -10 m/s/s and t=10 s

25. On takeoff, a rocket accelerates from rest at a rate of 50.0 m/s2 for exactly 1 minute. The rocket's speed after this minute of steady acceleration will be ____ m/s. a. 50.0 b. 500. c. 3.00 x 103 d. 3.60 x 103 e. none of these

Answer: C Use the equation vf= vi+ a*t vf = 0 + (50.0 m/s/s)*(60.0 s) = 3.00 x 103 m/s (Note that the unit on time must be the same as the time units for which the acceleration is given.)

Displacement

Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.

Distance

Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion.

20. What is the acceleration of a car that maintains a constant velocity of 55 mi/hr for 10.0 seconds? a. 0 b. 5.5 mi /hr/s c. 5.5 mi /s/s d. 550 mi/hr/s

If the velocity is constant, then there is no acceleration. That is, the value of the acceleration is 0.

Scalar

Scalars are quantities that are fully described by a magnitude (or numerical value) alone.

Speed

Speed is a scalar quantity that refers to "how fast an object is moving."

7. Which one of the following quantities is NOT a speed? a. 10 mi/hr b. 10 mi/hr/sec c. 35 m/s d. 20 m/s

b. 10 mi/hr/sec

19. The average speed of an object which moves 10 kilometers (km) in 30 minutes is ____. a. 10 km/hr b. 20 km/hr c. 30 km/hr d. more than 30 km/hr

b. 20 km/hr

22. A speedometer is placed upon a free-falling object in order to measure its instantaneous speed during the course of its fall. Its speed reading (neglecting air resistance) would increase each second by ____. a. about 5 m/s b. about 10 m/s c. about 15 m/s d. a variable amounte. depends on its initial speed.

b.The acceleration of gravity is approximately 10 m/s/s. Acceleration represents the rate at which the velocity changes - in this case, the velocity changes by 10 m/s every second. So the speed will increase by the amount of 10 m/s every second.

Velocity equation

displacement/time= velocity

18. Which one of the following statements is NOT true of a free-falling object? An object in a state of free fall ____. falls with a constant speed of -10 m/s. falls with a acceleration of -10 m/s/s. falls under the sole influence of gravity. falls with downward acceleration which has a constant magnitude.

falls with a constant speed of -10 m/s.

speed equation

s=d/t

Acceleration equation

velocity/time

Vector

Vectors are quantities that are fully described by both a magnitude and a direction.

Velocity

Velocity is a vector quantity that refers to "the rate at which an object changes its position.