Horizontal Projectiles Review

Horizontal Projectiles Review

First and foremost - kinematics equations

• d= v_it + 1/2at²

• v_fy = gt

Multiple Choice

A player kicks a ball across the field. At the very top, what is the acceleration of the ball?

• It is accelerating to the right

• There is no acceleration at the top

• 9.8 m/s² up

• 9.8 m/s² down

Multiple Choice

A soccer ball is kicked horizontally off a cliff. What information is needed to find the time to fall?

• The height of the cliff

• The initial speed of the ball

• The mass of the ball

• All of these

Multiple Choice

A marble traveling at 3 m/s rolls off the edge of a 1 m high table. What is its initial vertical speed?

• -10 m/s

• 0 m/s

• -3 m/s

• -15 m/s

Multiple Choice

Which best describes the vertical motion of a projectile, assuming no air resistance?

• Acceleration of -9.8 m/s²

• Accelerations of -5 m/s²

• An increasing acceleration every second

• Constant velocity

Multiple Choice

Which best describes the horizontal motion of a projectile, assuming no air resistance?

• Acceleration of -9.8 m/s²

• Acceleration of -5 m/s²

• An increasing acceleration every second

• Constant velocity

Poll

How comfortable are you solving horizontal projectile problems?

• Very comfortable

• I'm pretty sure I've got it

• I feel okay but not great

• I'm so confused please help (ask for help if this is you!)

Multiple Choice

What is the first step in solving a projectile problem?

• Two columns - x and y

• sketch it

• variable lists

• calculate time

The steps are (are these in your notes? why not?!):

• 1: Sketch it

• 2: x and y columns

• 3: variable lists - what do we know? what do we want to know?

• 4: acceleration - x=0 and y=g=-9.8 m/s/s

• 5: solve for time in y direction

• 6: copy time from y column to x column

• 7: use your kinematics equations to solve for the remaining variables

5 variables in each column - every time (write these down in your notes!)

• vertical and horizontal distance

• vertical and horizontal initial velocity

• vertical and horizontal final velocity

• vertical and horizontal acceleration

• time

Now, let's practice

Multiple Choice

A cannon is fired horizontally from a 5.0 m tall tower. How much time will it take until the projectile hits the ground?

• 0.5 s

• 1.0 s

• 2.0 s

• 5.0 s

Multiple Choice

If the cannonball from the previous question is fired with a horizontal velocity of 140 m/s, how far will it travel horizontally?

• 141.4 m

• 282.8 m

• 176.3 m

• 83.8 m

Multiple Choice

A Macaque monkey sitting 12 m up in a tree throws a nut horizontally at 11 m/s.

What is the final x velocity?

• can't tell

• 11 m/s

• 9.8 m/s

• -11 m/s

• -9.8 m/s

Multiple Choice

A Macaque monkey sitting 12 m up in a tree throws a nut horizontally at 11 m/s.

What is the initial y velocity?

• 9.8 m/s

• -9.8 m/s

• 11 m/s

• 0 m/s

Multiple Choice

How long will it take the nut to hit the ground?

• 2.45 s

• 4.32 s

• 1.56 s

• not enough information

Multiple Choice

The final requirement for a degree in geology is Field Camp, an 8 week field experience in which budding geologists must complete rigorous real-world mapping projects. To celebrate the end of field camp, one student threw his rock hammer off of a 78 m cliff with a horizontal velocity of 34 m/s. He was then reminded that he had one more day of field work, so he needed to go get his hammer. How far away from the cliff did he have to walk in order to find his hammer?

• 221.78 m

• 153.23 m

• 135.65 m

• 78.98 m

Poll

How comfortable are you solving horizontal projectile problems?

• Very comfortable

• I'm pretty sure I've got it

• I feel okay but not great (ask for help if this is you!)

• I'm so confused please help (ask for help if this is you!)