Download Name: Notes - 4.3 Newton`s Second Law of Motion: Concept of a

Name: ___________________________
Notes - 4.3 Newton’s Second Law of Motion: Concept of a System
1. What do we mean by a change in motion?
2. What causes the change in motion?
3. Figure 4.5 (b) - Adult Pushing the Child in the Wagon
A. Draw the free body diagram of all the forces involved.
B. Define:
F–
Fg –
FN –
Ff –
4. Acceleration is proportional to _______________.
5. The net external force Fnet is the vector sum of all external forces. List the two
methods that Fnet can be determined.
A. Graphically: _________________________
B. Analytically: _________________________
6. How is acceleration related to the mass of the system?
7. Newton’s 2nd Law
A. Write Newton’s 2nd Law in terms of net force.
Fnet =
B. Write Newton’s 2nd Law in terms of acceleration.
a=
8. Units of Force
A. Since the unit of mass is kilogram, the unit of acceleration is m/s2, and F = ma,
what are the units of force?
B. 1
kg m
=
s2
9. Weight:
A. The weight of an object (designated as w or Fg) is a force. Weight is not g (the
acceleration due to gravity). w = ____________
B. What is the weight of a 1.0 kg mass on Earth?
C. What is the weight of a 1.0 kg mass on the Moon?
10. What is the difference between mass and weight?
11. Bathroom Scales
A. What do bathroom scales measure? Mass or Weight?
B. Would the bathroom scale reading change if you were on the Moon? How?
12. Suppose that the net external force (push minus friction) exerted on a lawn mower is
51 N (about 11 lb) parallel to the ground. The mass of the mower is 24 kg. What is its
acceleration?
13. Calculate the magnitude of force exerted by each rocket, called its thrust T, for the
four-rocket propulsion system shown in Figure 4.8. The sled’s initial acceleration is 49
m/s2, the mass of the system is 2100 kg, and the force of friction opposing the motion is
known to be 650 N.