Unit3: Forces
What is Force ?
What is Importance of forces?
Think about Forces in our universe ?
What is the difference?
Contact force
Non- Contact force
What the forces can do?
1- Start movinn
2- stop moving
3- speed up,
4- slow down
5- change direction
6- changes in velocity
7- acceleration
Do this Simulation!
See this video
- A force : is any push or pull.
- Importance of forces.
Forces are what hold our world together – if it wasn’t for forces, our universe would
be flying apart
- SI Unit of Force: Newtons = 1 kg*1m/s^2;
- One newton is amount of force needed to accelerate 1 kgs of mass at 1 m/s^2.
- Force is a vector ( magnitude and direction )
- Force causes acceleration the magnitude and direction of the acceleration depend
on the magnitude and direction of the force (that is causing the acceleration).
- Balanced Forces: total Forces action on object = 0
- Unbalanced Forces : Total forces acting on object = / 0
** Note: Unbalanced forces cause acceleration.
FBD Definition
sketch of an object of interest with all the surrounding
objects stripped away and all of the forces acting on the
body shown.
Free Body Diagram
Normal Force:
• Normal force is a contact force. If two surfaces are not in
contact, they can't exert a normal force on each other
Frictional Force:
FBD and net forces
• A 50 kg person is skiing across the snow. The person pushes himself
forward with 400 N of force. The friction force between the person and
the snow is 300 N. What is the horizontal + vertical + total net force
acting on the person?
• A 50 kg person is being pulled on a sled across the snow. His Snow
Dogs pull with a force of 400 N at an angle of 30 degrees. The friction
force between the person and the ground is 300 N. What is the
horizontal + vertical + total net force acting on the person?