Question

1. which of these is an example of negative acceleration? *

a race car starting when the light turns green.
a bicycle applying its brakes to stop at a red light.
a train moving at the same, steady speed.
a cheetah sitting still under a tree.

1. which of these is an example of positive acceleration? *

a bicycle applying its brakes to stop at a red light.
a cat backing up from a barking dog.
a scooter cruising faster and faster as they dodge ebikes on the greenbelt.
a ladybug sitting still on a leaf.

Explanation:

Step1: Understand negative acceleration

Negative acceleration (deceleration) occurs when an object's speed decreases. A bicycle applying brakes to stop is slowing down, so its acceleration is negative.

Step2: Analyze other options for question 23

• A race car starting is increasing speed (positive acceleration).
• A train at steady speed has zero acceleration.
• A cheetah sitting still has zero acceleration.

Step3: Understand positive acceleration

Positive acceleration occurs when an object's speed increases. A scooter going faster and faster is accelerating positively.

Step4: Analyze other options for question 24

• A bicycle braking is negative acceleration.
• A cat backing up (assuming constant speed or slowing) is not positive acceleration (if constant speed - zero acceleration; if slowing - negative).
• A ladybug sitting still has zero acceleration.

Answer:

1. A bicycle applying its brakes to stop at a red light.
2. A scooter cruising faster and faster as they dodge ebikes on the Greenbelt.