First Law
A car is moving at a constant velocity down a road. Is there a nonzero net force acting upon it?
No. There is no net force acting upon an object that is not changing velocity.
What equation is used to describe Newton's second law?
F=ma
or
A=F/m
A man exerts a force of 300N downwards on the floor. What is the force the floor is exerting on him? (must include magnitude and direction)
300N upwards
A bug runs into a car windshield and sticks to it. What word is used to describe this type of collision, in which two colliding objects stick together? ( A __________ collision)
inelastic collision
What is the unit for momentum
kg m/s
A car moves at a constant speed around a circular track. Is its inertia changing?
yes, its inertia is changing because the direction of the velocity is changing
What is the Force of gravity acting on a 100kg man who is standing still on the street?
-980 N
A man pushes a box to the East with 100N of force, and it accelerates. What is the force of the box acting on the man? (include both magnitude and direction)
100N to the West
A 200 kg man has a velocity of 3m/s to the East. What is his momentum? (include both magnitude and direction)
600 kgm/s to the East
what is the term used to describe the velocity of an object in freefall when the net force acting on the object reaches zero and it stops accelerating downwards?
terminal velocity
An 10kg object falling through the air accelerates downwards at -9.8 m/s^2. Based on this, we can conclude that force of air resistance/drag on the object is:
0 m/s^2
An 8kg ball is accelerating at 5m/s^2. What is the net force acting on the ball?
40 N
A bowling ball and a feather are dropped inside a vacuum tube with no air resistance. Which object experiences a greater net force?
The bowling ball
Gravity is an attractive force between two massive objects, so an object with a greater mass experiences a greater force due to gravity.
Under which circumstance must the net momentum of a system change?
a) When the system is moving
b) when the system has a net force acting upon it
c) when two objects within the system change their individual momentums
d) The momentum of a system never changes.
b)when the system has a net force acting upon it
In a world without air resistance, if I drop a feather and a rock from the same height at the same time, which hits the ground first?
they hit at the same time
A net force is acting on an object. Which of the following must also be changing? Choose all that apply:
a) position
b) velocity
c) acceleration
d) momentum
e) gravity
b) velocity
d) momentum
A 10kg box is being pushed to the right with 2 N of force, and to the left with 8 N of force. There are no other forces acting on it. What is its acceleration? (include both magnitude and direction)
0.6 m/s^2 to the left
A 10 kg box is being pulled Eastward by a rope. It accelerates at 5 m/s^2. There are no other forces acting on the box.
What is the force that the box is exerting on the rope? (include both magnitude and direction)
50N to the West
A 90 kg man has a momentum of 450kgm/s to the North. What is his velcocity? (Include both magnitude and direction)
5 m/s North
A plane is flying and being blown by the wind. It experiences a force of 5N to the North, and 5N to the East. What is the net force experienced by the plane?
square root of 50 Newtons
Draw the chart representing the relationship between Change in velocity and net force.
Did its velocity change?
Yes / \ No
/ \
Nonzero net force Zero Net Force
I am pushing a 100 kg cart down the road with a force of 500 N. It accelerates at only 2 m/s^2. What is the force of friction acting on the cart? (there are no other forces besides my push and friction)
Friction exerts 300 N in the opposite direction to the direction of my pushing.
A heavy crate is being pulled by two ropes.
The first rope pulls with 2 N to the north. The second rope pulls with 5N to the East.
The box is not moving.
What is the net force that the box is exerting on the two ropes?
square root of 29 N
Box 1 has a mass of 5kg and is moving at 10m/s.
It runs into box 2, which has a mass of 2kg, and is at rest.
The two boxes stick together.
What is their final velocity?
7.14 m/s
Draw a Free Body Diagram for an airplane that is flying upwards at an angle.
(see whiteboard)