Chapter 1 Problems

What is 6 feet in m?

1.83 m 6 x 12 x 2.54 x (1/100)

A long distance runner has an average speed of 4 m/s during a race. How far does the runner travel in 20 min?

D= 4,800 m x - xo = Vt d= Vt d= 4 x 1200

What is 6 feet in cm?

182.88 cm 6 x 12 x 2.54

The quartz crystal used in an electric watch vibrates with a frequency of 32,768 Hz. What is the period of the crystal's motion?

3.05 x 10^-5 s F = 1/T --> T 1/F = 1/32,768 Hz

How far does a car going 25 m/s travel in 5s? How far would a jet going 250 m/s travel in 5s?

A) For car = 125 m B) For jet = 1250 m a) x = xo + Vt --> x - xo = vt --> x - xo = 25 x 5 = 125 m b) x -xo = Vt d = 250 x 5 d = 1250 m

A runner is going 10 m/s around a curve section of track that has a radius of 35 m. What is the runner's acceleration?

Ac = 2.86 m/s^2 Ac = V^2 / r = 10^2 / 35

A high performance sport car can go from 0 to 100 mph (44.7 m/s) in 7.9 s. a) What is the car's average acceleration? b) The same car can come to a complete stop from 30 m/s in 3.2 s. What is it's average acceleration?

a) 5.66 m/s^2 b) -9.38 m/s^2 a) a= v-vo / t a= 44.7 - 0 / 7.9 a= 44.7 / 7.9 b) a= v- vo / t a= 0-30 / 3.2 a= -30/3.2

A bungee jumper falls for 1.3 s before the cord begins to stretch. Until the jumper has bounced back up to the height, the elastic cord causes the jumper to have an average acceleration upward of 4 m/s. a) How fast is the jumper going when the bungee cord begins to stretch? b) How far below the diving platform is the jumper at the moment? c) How long after the bungee cord beings to stretch does the jumper reach the low point of drop? d) How far below the diving platform is the jumper at the instant the speed is zero?

a) Vf = -12.74 m/s b) d = -8.281 m c) t= 3.19 s d) -28.57 m a) Vf = Vi + at Vf = 0 + (-9.8)(1.3) b) d = Vi (t) + 1/2 (a)(t^2) d = 0 (1.3) + 1/2 (-9.8)(1.3^2) c) t = Vf - Vi/ a t = 0 - (-12.74) /4 d) D^2 = Vi (t) + 1/2 (a)(t^2) = -12.74 (3.19) + 1/2 (4)(3.19^2) = -40.64 + 20.35 = -20.29 (D + D^2) From part b = -8.281 - 20.29 = answer

A rock is dropped off the side of a bridge and hits the water below 2s later. a) what was the rock's velocity when it hit the water? b) What was the rock's average velocity as it fell? c) what is the height of the bridge above the water?

a) Vf = -19.6 m/s b) Vf= -9.8 m/s c) d = 19.6 m (no - because it is the height above the water) a) Vf = vi + at Vf = 0 + (-9.8)(2) b) Average Velocity = Vi + Vf / 2 = 0 + (-19.6 m/s) / 2 c) d = Vi (t) + 1/2 (a)(t^2) d = 0 + 1/2 (-9.8) (2^2)

A skydiver jumps out of a helicopter and falls freely for 3s before opening the parachute. a) What is the skydiver's downward velocity when the parachute opens? b) How far below the helicopter is the skydiver when the parachute opens?

a) Vf = -29.4 m/s b) d = -44.1 m a) Vf = vi + at = 0 + (-9.8) x 3 b) d = vi (t) + 1/2 (a)(t^2) d = 0 + 1/2 (-9.8)(3^2)

Initally stationary, a train has a constant acceleration of 0.5 m/s^2. a) what is it's speed after 15 s? b) What is the total time required for the train to reach a speed of 25 m/s?

a) Vf = 7.5 m/s b) t = 50 s a) Vf = vi + at = 0 + 0.5 x 15 b) Vf = vo + at --> t = Vf- Vi / a t = 25 - 0 / 0.5