Vertical Motion
An object is dropped from rest near the surface of the Earth. Assuming no air resistance, what is its acceleration (magnitude and direction) after 2 seconds?
-9.81 m/s2 or 9.81 m/s2 downward
In ideal projectile motion (ignoring air resistance), what is the value of the horizontal acceleration?
0 m/s2
Which contact force always acts perpendicular to the surface supporting an object?
Normal Force
According to Newton's First Law, how much is the net external force acting on an object moving at a constant velocity?
0 N
State Newton's Second Law of Motion as a formula relating force, mass, and acceleration.
ΣF⃗=ma
A ball is thrown vertically upward with an initial velocity of 29.4 m/s. How long does it take to reach its highest point?
t = 3.0 s
At what launch angle relative to the horizontal is the range of a projectile maximized on flat ground?
45 degrees.
What force vector should always be drawn pointing directly toward the center of the Earth on a free-body diagram?
Weight (Gravitational Force)
A 10 kg block rests motionless on a flat table. What is the magnitude of the normal force exerted by the table on the block?
98.1 N
If a constant net force of 20 N is applied to a 4 kg mass what is the resulting acceleration?
5 m/s2
What is the instantaneous velocity of a projectile at the exact peak of its vertical trajectory?
0 m/s
A package is dropped from an airplane flying horizontally at 100 m/s at an altitude of 500 meters. Neglecting air resistance, what is the package's horizontal velocity right before it hits the ground?
500 m/s
An object is sliding to the right across a rough horizontal floor. In which direction must the kinetic friction vector point on its free-body diagram?
To the left (opposite the direction of motion)
What term describes an object that is in equilibrium while moving at a non-zero, constant velocity?
Dynamic equilibrium
Identify the Newton's Third Law reaction force to a swimmer pushing backward against the wall of a pool.
The wall pushing forward on the swimmer.
A rock is dropped from a cliff and hits the ground after 4.0 seconds. How high is the cliff?
78.4 meters
A ball is launched with a velocity of 20 m/s at an angle of 30 degrees above the horizontal. Calculate its initial vertical component of velocity.
10 m/s
A box rests on an inclined plane angled at θ above the horizontal. Write the expressions for the components of the weight parallel and perpendicular to the incline.
Parallel: Wx=mgcosθ
Perpendicular: Wy=mgsinθ
A 50 N sign hangs symmetrically from two vertical ropes. What is the tension in each rope?
25 N per rope.
A 1000 kg car accelerates from rest to 20 m/s in 5 s. What net average force was required to produce this acceleration?
4000 N
An object is thrown upward at 20 m/s from a 50-meter high ledge. What is its speed right before it impacts the ground below?
37.1 m/s
A cannonball is fired at 50 m/s above the horizontal How far horizontally does it travel before returning to its launch height?
Approx. 241 m
An elevator accelerates upward while carrying a passenger of mass m. How does the magnitude of the Normal force (apparent weight) compare to the magnitude of the Weight on the passenger's free-body diagram?
The Normal force is larger than the Weight
**A 20 kg crate is held at rest on a 30 degree frictionless incline by a rope parallel to the incline. What is the tension in the rope?
98 N
**Two masses (m1=3kg, m2= 5kg) are connected by a light string over a frictionless pulley (an Atwood machine). What is the acceleration of the system when released from rest?
1.96 m/s2