Physics Lesson 3 Quiz

A student kicks a ball so that the ball's initial velocity is 8.3 m/s at 30°. How much time does the ball spend in the air?

0.9s Height of time (t) = 2vosin(theta)/g t = 2(8.3m/s)sin(30)/(9.8m/s^2) t = 0.9s

A student throws a rock horizontally off a 5.0 m tall building. The rock's initial speed is 6.0 m/s. How long will it take the rock to reach the ground? Air resistance is negligible.

1.0s

A student standing on the edge of a cliff throws a rock downward at a speed of 7.5 m/s at an angle 40° below the horizontal. It takes the rock 2.4 seconds to hit the ground. How far from the base of the cliff will the rock land?

13.8 m speed in x direction Vx = 7.5cos(40) Vx = 5.745m/s speed = d/t Vx = x / 2.4sec x = Vx * 2.4 x = 5.745 * 2.4 x = 13.8m

A person driving through a field has velocity components that are 30 m/s west and 20 m/s south. What is the approximate direction of the overall velocity?

214 tan^-1(20/30) = 0.6667 Theta = tan^-1(0.6667) = 34 180 + 34 = 214

A student runs off of a diving platform with a speed of 2.5 m/s and hits the water 0.8 seconds later. What is the height of the platform?

3.1 m

A person driving through a field has velocity components that are 30 m/s west and 20 m/s south. What is the magnitude of the overall velocity?

36 m/s

Which of the following is the closest approximation of the vertical component of a velocity that is 40 m/s at 80°?

39 m/s Vx = Vcos(theta) Vy = Vsin(theta) Vy = 40sin(80) Vy = 39m/s

A student standing on the edge of a cliff throws a rock downward at a speed of 7.5 m/s at an angle 40° below the horizontal. It takes the rock 2.4 seconds to hit the ground. How tall is the cliff?

39.8m h = vt + 1/2gt^2 vsin(40) = 7.5sin(40) = 4.82m/s h = (4.82)(2.4) + 1/2(9.8)(2.42) h = 39.8m

A student runs off of a diving platform with a speed of 2.5 m/s and hits the water 1.8 seconds later. What is the student's horizontal distance from the platform when she hits the water? Air resistance is negligible.

4.5 m

A student kicks a ball off the ground such that the ball has an initial speed of 17 m/s at some angle. Which of the following starting velocity angles will result in the greatest horizontal distance?

40°

Vector A has components A = <-2, 5> m/s and vector B has components B = <6, -2> m/s. What is the magnitude of vector C if C = A + B?

5 m/s 4i + 3j a^2 + b^2 = c^2 4^2 + 3^2 = c^2 16 + 9 = c^2 25 = c^2 c = 5

A student launches a small 0.5 kg rocket with an initial speed of 30 m/s at an angle of 60°. Approximately how much time will the rocket spend in the air? Air resistance is negligible

5.3s t = 2vosin(theta)/(g) t = (2)(30)sin(60)/(g) t = (2)(30)sin(60)/(9.8) t = 5.3s

A student kicks a ball so that the ball's initial velocity is 12 m/s at 60°. What is the maximum height of the ball?

5.5 m Voy = Vosin(theta) (12)(sin(60)) Voy = 10.39 y = (10.39)^2 /(2*9.8) = 5.5m

The grid below shows two vectors <strong>A</strong> and <strong>B</strong>. What is the magnitude of the sum of the vectors <srong>A</strong>+<strong>B</strong>?

5.7m

Suppose that an airplane flying 70 m/s at a height of 300 m drops a crate. What horizontal distance will the crate have traveled when it hits the ground? Assume negligible air resistance.

548m or 546m y = Yo + Voyt - 1/2gt^2 0 = 300 - 1/2(9.8)t^2 0 = 300 - 4.9t^2 -300 = -4.9t^2 T^2 = sqrt(61.2) t = 7.8s (70m/s)(7.8s) = 546m

The grid below shows the path a student takes through a campus area. What is the approximate direction of the student's overall displacement? (Be careful—this is not a position vs. time graph.)

56 tan^-1(6/4) = 56

An airplane in the process of taking off travels with a speed of 80 m/s at an angle of 15° above the horizontal. What is the ground speed of the airplane?

77 m/s Voy = Vsin(15) Voy = 80sin(15) Voy = 20.7m/s Vox = tan(15) = 20.7/Vox Vox = 77m/s

The grid below shows the path a student takes through a campus area. What is the approximate magnitude of the student's overall displacement? (Be careful—this is not a position vs. time graph.)

7m a^2 + b^2 = c^2 6^2 + 4^2 = c^2 36 + 16 = c^2 sqrt 52 = sqrt c c = 7

Which of the following best indicates the components of a vector that measures 30 m at 135°?

<-21, 21> m cos(135) = x/30 x = -21 (-21) + b^2 = (30)^2 441 + b^2 = 900 b^2 = 459 b = 21

A student rolls two balls off of a table. Ball A has twice the mass of ball B. Both balls leave the table with the same starting velocity. Which ball will land further away from the table?

A and B will land the same distance from the table.

A student rolls two balls off of a table. Ball A has twice the mass of ball B. Both balls leave the table at the same time with the same starting velocity. Which ball will hit the ground first?

A will hit the ground at the same time as B.

A student rolls two identical balls off of a table. Both balls leave the table at the same time, but ball B has twice the starting velocity. Which ball will hit the ground first ?

A will hit the ground at the same time as B.

A student kicks a ball that is initially at rest on the ground. The ball leaves the student's foot with some velocity v at an angle θ. When the ball is at its maximum height, which statement is most accurate?

At the maximum height, the velocity of the ball is zero.

A plane flying overhead releases a package. A stationary observer watches the path of the package as it falls. Which of the following paths will the observer see assuming negligible air resistance?

B (straight line)

A ball is attached to the center of the ceiling inside of a van moving at constant speed. If the ball is released, where will the ball land?

Directly below its starting position (middle of the van)

An airplane flies horizontally at a constant speed. The plane releases a package. If air resistance is negligible, where will the package land? Explain your answer.

Directly below the airplane

Which of the following is an example of a vector measurement?

Displacement, Velocity, and Acceleration.

A student fires a bullet horizontally from a gun. Which statement is most accurate?

The bullet will start to fall as soon as it leaves the gun.

Which of the following statements about projectile motion is/are true assuming negligible air resistance?

The horizontal component of the initial velocity is constant.

A student launches a rocket with some initial velocity v at some angle θ. The rocket hits a wall on its way back down to the ground. (See the diagram below.) Which of the following statements is most accurate?

The speed of the rocket just before it hits the wall is less than the starting speed of the rocket.

A student fires a bullet horizontally out of a gun. At the same time the bullet leaves the gun, the student drops a second bullet from the same height. Which bullet hits the ground first?

The two bullets will hit the ground at the same time.