Unit 2 – Linear Motion – Example Problems with Solutions
PROBLEM SOLVING GUIDELINES
• Make a list of given quantities (Data)
• Convert units if needed
• Make a sketch if necessary
• Identify the concept of what is to be determined
• Always solve the equation for the unknown
• Be consistent with units
• Check that the answer seems reasonable
1. A car moves at 50 km/h for 1 h and then at 60 km/h for 2 h.
a. How far did it go?
Given:
v1 = 50 km/h, t1 = 1 h
v2 = 60 km/h, t2 = 2 h
x1 = v1(t1) = 50(1) = 50 km
x2 = v2(t2) = 60(2) = 120 km
xtotal = 50 + 120
= 170 km
b. What was its average velocity for the entire trip?
v
x 170

= 56.6 km/h
t
3
2. A car comes to a stop in 6 s from a velocity of 30 m/s.
a. What is its acceleration?
v f  v o 0  30

= - 5 m/s2
t
6
b. At the same acceleration, how long would it take the car to come to a stop from a velocity of 40 m/s?
v f  v o 0  40
t

=8s
a
5
3. A stone is dropped from the edge of a cliff.
a. What is its velocity in meters per second 3 s later?
vf = vo + gt
= 9.8 (3)
= 29.4 m/s
b. How far does it fall in this time?
x = vot + ½ gt2
= ½ (9.8)(3)2
= 44.1 m
4. Find the acceleration of a car that comes to a stop from a velocity of 60 m/s in a distance of 360 m.
v f 2  v o 2  2ax
v f 2  v o2
 - 5 m/s2
2x