Unit 3 Exam Reveiw

Unit 3 Exam Reveiw

by Bill Longley

Multiple Choice

Two people fire two different guns simultaneously. One fires at 300m/s and the other at 100m/s. How is the vertical component (how far it falls) affected?

• The faster bullet will take less time to drop.

• The slower bullet will take less time to drop

• Neither bullet will drop

• the vertical component is not affected

​X vs Y

Remember that the Horizontal is independent from the Vertical. Therefore no matter the horizontal speed it has no bearing on how fast it will drop to the ground.​

Multiple Choice

What happens to the horizontal velocity of a projectile when fired from a cannon?

• The projectile maintains speed

• The projectile slows down

• the projectile speeds up

• The projectile ceases to exist

​Horizontal Velocity

​In order to be a projectile there ca be no thrusts or rotors on the object to allow additional force.

​The only force is gravity.

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​Therefore there is no acceleration in the horizontal direction thus it does not slow down or speed up. It maintains velocity until it hits the ground.

Multiple Choice

An elephant and an Ant fall to their doom. In the absence of air friction who hits the ground first?

• The Elephant hits the ground first due to its mass

• The ant hits the ground first due to its smaller size

• They both hit the ground at the same time.

​Gravity

​All objects will fall at the same rate in the absence of air. No matter the object. The only way for two objects to hit the ground at different times is for them to begin at different heights.

Multiple Choice

What is the shape of this trajectory?

• Arc

• Semi-circle

• Parabolic

• Trianglular

​Parabolic Motion

​due to the nature of gravity and acceleration, the lines drawn (trajectory) of a projectiles path will always follow a distorted curve known as parabolic motion.

Multiple Choice

If you drop a rock off this bridge and use a stopwatch to see how long it is in the air, is that enough information to see how tall the bridge is?

• No. You need to know initial velocity, final velocity, acceleration, and time

• Yes, this is enough information

​Calculating Vertical

Multiple Choice

What is the horizontal acceleration of the ball before it hits the ground?

• 9.81 $$\frac{m}{s^2}$$  

• 9.81 m/s

• 0 m/s

• $$0\frac{m}{s^2}$$  

Multiple Choice

What is the Vertical acceleration of the ball before it hits the ground?

• 9.81 $$\frac{m}{s^2}$$  

• 9.81 m/s

• 0 m/s

• $$0\frac{m}{s^2}$$  

Multiple Choice

What is the Vertical Velocity of the ball at the top of its flight?

• 9.81 $$\frac{m}{s^2}$$  

• 9.81 m/s

• 0 m/s

• $$0\frac{m}{s^2}$$  

​Projectile Motion Properties

​A projectile as stated previously only has gravity as a force.

​Therefore,

• There can be no horizontal acceleration at any point in it's flight

• ​The vertical acceleration will always be due to gravity

• ​The vertical velocity will be the same going up and going down

• ​The vertical velocity at the height will be 0 m/s

Multiple Choice

A lifeguard spins a whistle on a string around his hand counterclockwise. If they let go at the point as shown in the image, which direction will the whistle fly?

• Towards the center

• Straight up

• straight down

• curved to the right

Circular motion​

​An object will always leave a circular path tangent to its motion. which is perpendicular to the radius at the point that it touches the edge of the circle or curve.

​Thanks for going over the review

​Thanks for making it this far and studying. for your effort the phrase to memorize is:

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​The monkey loves bananas

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