A compact car travels along a straight test track. Its position x (measured from the start line) is recorded at three instants, shown below.
Numerical data (all distances in metres, all times in seconds):
• t=0: x=12
• t=4: x=68
• t=9: x=104
Answer the following questions. Show all reasoning, include units with numerical answers, and state any assumptions you make.
(1) Calculate the car’s average velocity during the interval 0≤t≤4s.
(2) Using your result from part (a), determine the car’s average acceleration during the entire interval 0≤t≤9s.
(3) Describe in words what the sign and magnitude of your answer in part (b) tell you about how the car’s motion is changing over time.