Gravity and Velocity: Quiz Examples

Question 1

The cat sprite is in the air and NOT touching the ground. What happens?

when green flag clicked
forever
  if <not <touching [ground v]?>> then
    change y by [-5]
  end

Answer: The cat falls down by 5 each frame. Since the cat is not touching the ground, touching ground is false, and not flips it to true, so the change y by -5 runs.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 2

The cat sprite IS touching the ground. What happens?

when green flag clicked
forever
  if <not <touching [ground v]?>> then
    change y by [-5]
  end

Answer: Nothing happens. The cat is touching the ground, so touching ground is true. not true is false, so the code inside the if does not run. The cat stays where it is.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 3

What is the value of velocity after 3 frames if the cat is in the air the entire time?

when green flag clicked
set [velocity v] to [0]
forever
  if <not <touching [ground v]?>> then
    change [velocity v] by [-1]
  else
    set [velocity v] to [0]
  end
  change y by (velocity)

Answer: Velocity is -3. Each frame, velocity decreases by 1: after frame 1 it’s -1, after frame 2 it’s -2, after frame 3 it’s -3. This makes the cat fall faster over time, simulating real gravity.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 4

The cat is touching the ground and velocity is currently -8. What happens on the next frame?

when green flag clicked
set [velocity v] to [0]
forever
  if <not <touching [ground v]?>> then
    change [velocity v] by [-1]
  else
    set [velocity v] to [0]
  end
  change y by (velocity)

Answer: Velocity is reset to 0. Since the cat is touching the ground, the else branch runs and sets velocity to 0. Then change y by 0 does nothing, so the cat stays on the ground.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 5

The cat is touching the ground and the player presses space. What happens?

when [space v] key pressed
if <touching [ground v]?> then
  set [velocity v] to [10]
end

Answer: Velocity is set to 10. Since the cat is touching the ground, the condition is true, so velocity becomes 10. On the next frame, change y by 10 will move the cat upward — this is the jump.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 6

The cat is in the air (NOT touching the ground) and the player presses space. Will the cat jump?

when [space v] key pressed
if <touching [ground v]?> then
  set [velocity v] to [10]
end

Answer: No. The cat is not touching the ground, so touching ground is false. The code inside the if does not run, and velocity is not changed. This prevents the cat from jumping in mid-air.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 7

The cat just jumped and velocity is 10. The cat is now in the air. What is velocity after 2 frames?

when green flag clicked
set [velocity v] to [0]
forever
  if <not <touching [ground v]?>> then
    change [velocity v] by [-1]
  else
    set [velocity v] to [0]
  end
  change y by (velocity)

Answer: Velocity is 8. Starting at 10, it decreases by 1 each frame: after frame 1 it’s 9, after frame 2 it’s 8. The cat is still moving upward but slowing down — just like a real jump.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 8

Why does using a velocity variable create smoother gravity than change y by [-5]?

The two options are side-by-side here for comparison:

change y by [-5]

change [velocity v] by [-1]
change y by (velocity)

Answer: With fixed gravity, the cat always falls at the same speed (-5 every frame). With velocity, the cat starts falling slowly and gets faster over time (-1, -2, -3, -4…). This simulates acceleration and looks more realistic, like real-world gravity.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 9

What is wrong with this gravity code? What will happen when the cat lands on the ground?

when green flag clicked
set [velocity v] to [0]
forever
  if <not <touching [ground v]?>> then
    change [velocity v] by [-1]
  end
  change y by (velocity)

Answer: The code is missing the else block that resets velocity to 0. When the cat lands on the ground, velocity will stay at whatever negative value it reached. The change y by (velocity) will keep pushing the cat downward through the ground.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.9

Question 10

The cat is on the ground and the player presses space. Trace through the code and describe what happens over the next 4 frames. Assume the cat leaves the ground after frame 1.

when [space v] key pressed
if <touching [ground v]?> then
  set [velocity v] to [10]
end

when green flag clicked
set [velocity v] to [0]
forever
  if <not <touching [ground v]?>> then
    change [velocity v] by [-1]
  else
    set [velocity v] to [0]
  end
  change y by (velocity)

Answer: Frame 1: Space sets velocity to 10, cat moves up by 10 and leaves the ground. Frame 2: Cat is in the air, velocity changes to 9, cat moves up by 9. Frame 3: Velocity changes to 8, cat moves up by 8. Frame 4: Velocity changes to 7, cat moves up by 7. The cat rises but slows down each frame, just like a real jump arc.

Standards: MS-CS-FCP.3.2, MS-CS-FCP.4.5, MS-CS-FCP.4.9