Unit3_assignment PHY.docx - PHY 1001 Unit Three – Forces...

PHY 1001
Unit Three – Forces and Newton’s Laws of Motion
Mathematical Assignment
1. The mass of a train is 30,000 kg. If the train accelerates at 1.1 m/s 2 ,
what net force (in Newtons) acts on the train?
Key Idea Stock of Data and
F ma 
2
30,000
1.1 /
m kg
a m s


Solution
2
30000 1.1 /
33,000
F kg m s
F N
 

Sanity Check
Unit analysis:
2
m
unit of F kg N
s
  
Estimation of magnitude:
30000 1.1
33,000
F
F
 

2. What is the weight (in Newtons) of a 1 kg object?
Key Idea Stock of Data and
W mg 
2
1
9.8 /
m kg
g m s


Solution

2
1 9.8 /
9.8
W kg m s
W N
 

Sanity Check
Unit analysis:
2
m
unit of W kg N
s
  
Estimation of magnitude:
1 9.8
9.8
W
W
 

3. A rocket with a mass of 4,000 kg has an engine that exerts a force of
40,000 N. What is the rocket's acceleration (in m/s 2 ) at take-off?
Key Idea Stock of Data and
F ma
F
a
m


4000
40,000
m kg
F N


Solution
2
40,000
4000
10 /
N
a
kg
a m s


Sanity Check
Unit analysis:
2
2
/
/
N kgm s
unit of a m s
kg kg
  
Estimation of magnitude:

40,000
4000
10
a
a
