Forces in 2D
2nd Law
Tilted Forces
1.
A hand pulls on a cart with an applied force, Fa = 5 N [Left] and a string pulls
on the same cart with a tension force which is directed [Right 30o Up]. The
cart remains at rest on a level surface.
a) Draw an ID, FD and Fnet statements (in x and y direction)
b) Determine the tension force
c) Create this situation using two spring scales and a cart to confirm
d) Also use the mass of the cart to calculate the Normal Force
e) Is the normal force always the same size as the force of gravity?
Forces on a Tilt (aka ramp, aka incline)
2.
A cart is at rest on a surface inclined at an angle of 30 degrees to the
horizontal. It is held in place by a force, Ft.
a) Draw an ID, and FD
b) How should you orient your coordinate system? Why?
c) Draw any components for vectors that aren't parallel to either axis
Choosing a coordinate system
●
●
●
●
Any coordinate system will work, but some choices make it easier to
understand
The best choice is often the one that lines up with the direction that the object
moves (or would move if allowed to)
If a force is not parallel to either axis, dashed component vectors should be
drawn
Make sure component vectors are parallel to each axis of the coordinate
system.
Forces on a Tilt (aka ramp, aka incline)
2.
a)
b)
c)
A cart is at rest on a surface inclined at an angle of 30 degrees to the
horizontal. It is held in place by a force, Ft.
Which Force Diagram
is correct?
Which forces (or
components of a force)
balance out?
What misconception
occurs in the incorrect
diagram?
Forces on a Tilt (aka ramp, aka incline)
2.
A cart is at rest on a surface inclined at an angle of 30 degrees to the
horizontal. It is held in place by a force, Ft.
The angle of the ramp is labelled. If the ramp is at a 30 degree
angle, what is the angle of the components of Fg (labelled with “?”)
Forces on a Tilt (aka ramp, aka incline)
2.
A cart is at rest on a surface inclined at an angle of 30 degrees to the
horizontal. It is held in place by a force, Ft.
Now, determine the acceleration of the cart if the string is cut.
Remember: The force of gravity acting on an object with mass, m, can be
found using the expression: Fg = mg, where g = 9.8 N/kg and is called the
gravitational field strength. Be careful not to confuse this expression with
Fnet = ma.
Practice
Components and Force Diagrams Worksheet
Textbook:
P75 #9a,b
P80 #6ab
P92 #6,7
P96 #9
P117 #9,10
ALSO: Quiz Thurs - 2D Forces (Draw Force Diagrams, Fnet Statements, Solve unkowns)