Physics 202A FIRST EXAM Chapters 1 - 3 Spring 2013
1
Name:___________________________________
Solve the following problems in the space provided. Use the back of the page if needed. Each problem is
worth 20 points. You must show your work in a logical fashion starting with the correctly applied
physical principles. The equations you need are on the equation sheet. Your score will be maximized if
your work is easy to follow because partial credit will be awarded.
1. The velocity versus time graph for a stunt car is
shown at the right. Answer the following questions.
Be sure to explain you reasoning for full credit.
a. Find the velocity at t = 1.0s
Reading the graph, v = 20m/s.
b. Find the velocity at t = 4.0s
Reading the graph, v = 40m/s.
c. Find the velocity at t = 8.0s
Reading the graph, v = 20m/s.
d. Find the average velocity between t = 0s and t = 2.0s
The initial velocity is zero and the final velocity is 40m/s, so on average the car is moving 20.0m/s.
e. Find the instantaneous acceleration at t = 1.0s
The instantaneous acceleration is the slope of the velocity vs. time graph so,
a=40 −0
2−0
⇒
a=20 m
s2
.
f. Find the instantaneous acceleration at t = 4.0s
The instantaneous acceleration is the slope of the velocity vs. time graph so,
a=0−0
6−2
⇒
a=0m
s2
.
The graph is flat, so the slope is zero.
g. Find the instantaneous acceleration at t = 8.0s
The instantaneous acceleration is the slope of the velocity vs. time graph so,
a=0−40
10 −6
⇒
a=−10 m
s2
.
h. Find the average acceleration between t = 0s and t = 2.0s.
The average acceleration is
a=∆v
∆t
=40 −0
2−0
⇒
a=20 m
s2
.
i. Find the average acceleration between t = 0s and t = 6.0s.
The average acceleration is
a=∆v
∆t
=40 −0
6−0
⇒
a=6.7 m
s2
.
j. Find the average acceleration between t = 0s and t = 10.0s.
The average acceleration is
a=∆v
∆t
=0−0
10 −0
⇒
a=0m
s2
.
