PHY.151 TEST #1 REVIEW
1. To get to her physics class, Alice walks 0.25 mi to the bus stop. She takes the bus 1.2 mi to the train station. She takes the train 13 mi and walks the remaining 0.17 mi to her class. How far is her commute expressed to the correct number of significant figures?
.25+13+1.2+.17=14.62 or 15?????
A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory, what is the ball's acceleration? What is the ball's velocity?
1. Acceleration is 9.8 m/s2 downward. Velocity is horizontal component of initial velocity.
A boy throws a rock with an initial velocity of 3.13 m/s at 30.0° above the horizontal. How long does it take for the rock to reach the maximum height of its trajectory?
t= .16 s
1. A celebrating student throws a water balloon horizontally from a window 50 m above the ground. It hits the ground 60 m from the building. a) What is the horizontal component of the velocity of the balloon just before it hits the ground? b) What is the magnitude of the vertical velocity of the balloon just before it hits the ground?
1. horizontal v =Δx / Δt = 60m/3.194s = 18.8 m/s; b) vertical v = at = (-9.8m/s2)(3.194 s) = 31.3 m/s
A kid throws a water balloon horizontally, with a velocity of 15 m/s, out his second story window. It falls 20 m to the ground. How far (in m) will the balloon hit from the vertical side of the building?
30 m
1. A train travels at a constant speed of 60.4 mi/h for 101.5 min. What distance does the train cover expressed to the correct number of significant figures?
60.4 X 101.5 Distance=velocity x time = ------------- = 102.17 60.4
1. A vector A has components Ax = 12.0 m and Ay = -5.00 m. a) What is the angle that vector A makes with the +x-axis? b) What is the magnitude of vector A?
A) tan^-1 (-5/12)=-22.62 B) Mag= sq rt of Ax^2+Ay^2= 12^2+-5^2= 13
A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will
Directly over the package. When the package drops, the plane and package both have horizontal velocity component.
If A + B = 0, do the vectors A and B have equal magnitudes and point in the same direction?
False
If a vector pointing upward has a positive magnitude, does a vector pointing downward have a negative magnitude?
No magnitude is always positive because it is a direction.
Jeff ran up a hill at 7.0 m/s. The horizontal component of his velocity vector was 5.1 m/s. What was the vertical component of his velocity?
V= Vx^2 + Vy^2 over sq root. Horizontal comp= 5.1 = X Vy^2= 7^2 - 5.1^2=22.99 Sq root of 22.99= 4.7948
James and John dive from an 2 m overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. If there is no air resistance, when they reach the lake below
horizontal V= 0 Veritcal Vi=0
A projectile leaves the ground at 150 m/s and reaches a maximum height of 0.57 km. If there was no air resistance, at what angle above the horizontal did it leave the ground?
v= 150 H= max height= .57km Vy^2= Vy^2 -2gh 0^2= V^2sin^2-2gh Sin^2= 2gh/v^2= 2x9.8x570/150(2) Sin^2=.49653 sin= sq root .49653 inverse it sin-1=(.70)= 44.8 degrees
