Phys101
Term: 123
Online HW-Ch02-Lec01
Q1:
A graph of position versus time for a certain particle moving along the x-axis
is shown in figure. Find the average velocity in the time intervals from 2.00 s
to 4.00 s:
A. 5.00 m/s
B. 1.25 m/s
C. -2.5 m/s
D. -3.33 m/s
E. 0
Ans:
vavg =
x(m)
10
8
6
4
2
0
1
-2
-4
-6
2
3
4
5
6
7
8
t(s)
x2 − x1
5 − 10
=
= −2.50 m/s
4−2
t 2 − t1
Q2:
A person travels by car from one city to another with different constant speeds
between pairs of cities. He drives for 30.0 mins at 80.0 km/h , 12.0 min at 100 km/h,
and 45.0 min at 40.0 km/h and spends 15.0 min eating lunch and buying gas.
Determine the average speed for the trip.
Ans:
∆x1 = v1 ∆t1 = (80)(0.5 h) = 40.0 km
∆x2 = v2 ∆t 2 = (100)(0.2 h) = 20.0 km
∆x3 = v3 ∆t 3 = (40)(0.75 h) = 30.0 km
Q3:
Savg =
40 + 20 + 30
0.5 + 0.2 + 0.75
= 52.9 km/h
A race car moves such that its position fits the relationship x(t) = 5.00 t +0.75 t3 where
x is measured in meters and t in seconds. Determine the instantaneous velocity of the
car at t = 5.00 s ?
Ans:
t = 5 seconds
v=
dx
= 5.00 + 2.25t 2 = 61.3 m/s
dt
KFUPM-Physics Department
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