Download Chapter 4: Forces & Newton's Laws Example Questions & Problems F

Chapter 4: Forces & Newton's Laws
Example Questions & Problems
Fnet  F1  F2 
 Fn
a
Fnet
m
FAB  FBA
Example 4.1
a. Forces are shown on two objects. For each figure, draw and label the net (i) net force vector
and (ii) acceleration.
b. In the figures below, one force is missing. Use the given direction of acceleration to
determine the missing force and draw it on object.
Example 4.2
For each, (i) draw a motion diagram and state whether it is equilibrium or nonequilibrium, (ii) draw
a FBD and break the forces into components and (iii) sum them according to Newton’s 2nd law.
a. An elevator, suspended by a single cable, has just left the tenth floor and is speeding up as
it descends toward the ground floor.
b. A rocket is being launched straight up. Air resistance is not negligible.
c. A heavy box is in the back of a truck. The truck is accelerating to the right. Apply your
analysis to the box.
Example 4.3
For each, (i) draw a motion diagram and state whether it is equilibrium or nonequilibrium, (ii) draw
a FBD and break the forces into components and (iii) sum them according to Newton’s 2nd law.
a. A heavy crate is being lowered straight down at a constant speed by a steel cable.
b. A bicycle is speeding up down a hill. Friction is negligible, but air resistance is not.
c. You've slammed on your car brakes hill going down a hill. The car is skidding to a halt.
Example 4.4
The fastest pitched baseball was clocked at 46 m/s. If the pitcher exerted his force (assumed to
be horizontal and constant) over a distance of 1.0 m, and a baseball has a mass of 145 g.
a. Draw a FBD of the ball during the pitch.
b. What force did the pitcher exert on the ball during this record-setting pitch?
c. Estimate the force in part (b) as a fraction of the pitcher's weight.