Chapter 2.4-2.6

In the absence of air resistance two balls are thrown upward from the same launch point. Ball A rises to a maximum height above the launch point that is four times greater than that of ball B. The launch speed of ball A is ________ times greater than that of ball B.

two (v2 = v02 + 2ax, with v = 0 m/s)

The left ventricle of the heart accelerates blood from rest to a velocity of +29.3 cm/s. (a) If the displacement of the blood during the acceleration is +2.48 cm, determine its acceleration (in cm/s2). (b) How much time does blood take to reach its final velocity?

v22-v12=2as a = ( v22-v12)/(2s) = 262/4 = 169 cm/s2 so Δv=at and t =(v2-v1)/a = 26/169 = 0.154 s

A boy jumps from rest, straight down from the top of a cliff. He falls halfway down to the water below in 0.765 s. How much time passes during his entire trip from the top down to the water? Ignore air resistance.

1.08s H/2= 0x0.765s + 1/2 x 10 (0.765^2) T^2= 5.85/5

An airplane starts from rest and reaches a takeoff velocity of 60.0 m/s due north in 4.0 s. How far has it traveled before takeoff?

120 m, due north [x=1/2(V0+V)t]

High-performance race cars can accelerate from 0 m/s to 27 m/s (60 mi/h) in about 4 s. To see how large the acceleration due to gravity is, determine the time required for an object dropped from rest to attain a speed of 27 m/s. Ignore air resistance.

2.8 s (v = v0 + at)

Of the five kinematic variables, how many must be known before the equations of kinematics can be used to determine the unknown variables in a problem that deals with a single moving object?

3

Two cars both start from rest and have the same constant acceleration. When radar is used to measure the velocity of each car, car A is found to be moving twice as fast as car B. At the instant the radar is used, car A has a displacement that is ______ times as great as the displacement of car B. eight The cars have same displacement. two four

4 (v2 = v02 + 2ax, with v0 = 0 m/s)

A spacecraft is traveling with a velocity of +3250 m/s. Suddenly the retrorockets are fired, and the spacecraft begins to slow down with an acceleration whose magnitude is 10.0 m/s2. How far does the spacecraft travel until it comes to a momentary halt?

5.28 × 105 m (v2 = v02 + 2ax)

What constant acceleration would a car, starting from rest, have to sustain in order to reach a velocity of 27 m/s due east in 3.0 s?

9.0 m/s2, due east (v = v0 + at)

Which one of the following statements is not true? Near the earth's surface the acceleration due to gravity has the approximate magnitude of 9.80 m/s2, points downward when the motion is downward, and points upward when the motion is upward. In free-fall motion near the earth's surface the acceleration is the acceleration due to gravity. In the absence of air resistance the motion of a baseball dropped from rest from the top of a building is an example of free-fall. In the absence of air resistance the motion of a baseball after being thrown straight upward from the ground is an example of free-fall. The equations of kinematics apply to free-fall motion.

Near the earth's surface the acceleration due to gravity has the approximate magnitude of 9.80 m/s2, points downward when the motion is downward, and points upward when the motion is upward.

An astronaut on a distant planet wants to determine its acceleration due to gravity. The astronaut throws a rock straight up with a velocity of +12.3 m/s and measures a time of 18.0 s before the rock returns to his hand. What is the acceleration (magnitude and direction) due to gravity on this planet? (positive = up, negative = down)

T a =T/2 T a = 24.5s/2 = 12.3 ​

A ball is thrown vertically upward, which is the positive direction. A little later it returns to its point of release. The ball is in the air for a total time of 8.14 s. What is its initial velocity? Neglect air resistance.

[(8.14s)(9.8 m/s^2)]/2

A VW Beetle goes from 0 to 47.0 mi/h with an acceleration of +2.35 m/s2. (a) How much time does it take for the Beetle to reach this speed? (b) A top-fuel dragster can go from 0 to 47.0 mi/h in 0.750 s. Find the acceleration (in m/s2) of the dragster.

a) Δt=(v-v0/a) b) a=(v-v0/t-t0)

What are the 5 equations of kinematics

displacement velocity acceleration time

Which one of the following is not a kinematic variable that appears in the equations of kinematics? displacement velocity speed acceleration time

speed