Chapter 9: Interactions Flashcards
(32 cards)
what does W stand for?
- weight/ gravitational force acting on an object
what does G stand for?
gravitational field strength acting on the object
what does M stand for?
Mass of an object
How do you find Weight?
w = mg
- ( triangle w at the top and at the bottom is m and g )
what is pressure and its si unit
Pressure is the force exerted on an unit area
Pa
what are contact and non contact forces
contact forces- friction and elastic force
non-contact- gravitational and magnetic force
how do you find pressure?
Pressure = Force divided by Contact Area
- ( for triangle force is on top while p and c is at the bottom )
when does pressure increase?
- when the contact area is smaller
- when contact area is larger, there is less pressure exerted
- When there is more force applied
what is the si unit for force?
N
Why would someone be more likely to get hurt if they step on a nail, but be completely fine if they lie on a bed of nails?
The bed of nails have a significantly larger area of contact. The same force ( the person’s height ) will produce a much lower pressure if she lies on the bed, reducing injury.
- ( basically the larger the contact area, the more pressure produced )
is force and mass related?
No!! Thus if force is reduced, mass will not be affected.
What is a pivot?
It is the location/ point of contact.
- ( a turning effect MUST have a pivot. )
Does the length of a lever ( something that helps to exert force ) affect the force needed to do something?
Yes!! The longer the lever is, the less force is needed.
referring to page 13,
Explain how the application of a force can help one to remove the lid of the tin can easily.
- When the screwdriver is wedged between the tin can and the lid, it acts as a lever.
- When the screwdriver is pushed down, the downwards force creates a turning effect about the pivot
- This results in an upwards force applied on the lid, prying the lid open.
keywords: lever, downwards force creates a turning effect about the pivot, upwards force is applied
If there were 4 people and they were standing at various heights, in order, who would be experiencing the most pressure. ( 1 is the lowest 4 is the highest )
1 - most pressure
2
3
4 - least amount of pressure.
1 experiences the most pressure due to them experiencing the most amount of air particles
note: air particles has mass
Why are suction cups able to stick onto the wall?
- When a suction cup is suck onto the wall, air is pushed out from under the suction cup. The air pressure between the suction cup and the surface decreases. It becomes lower than the atmospheric pressure
- The higher atmospheric pressure hold the suction cup in place.
How do you find work done?
Force x distance moved in the same direction as the force
W at the top of the triangle then F | D
Is there any work done if someone is carrying a box and held it in a fixed position?
There is no work done!! Although there is force applied to hold the box in a fixed position, the box did not move in the direction as the force!
If a box is pushed and moves forward, would any work be done?
There is work done!! The force moved the box in the same direction as the force applied. Work is done to move the box forward.
If a box is lifted vertically from the floor, would there be any work done?
There is work done!! An upwards force is applied to lift the box in the same direction as the force.
Work is done to lift the box up.
If a box is carried and moved forwards, would there any work done in moving the box.
There is no work done!! The distance moved by the box was not in the same direction as the force applied to carry the box.
If Tessa dashes horizontally 30 m, and her bag weighs 60 N, what is the work done by Tessa while carrying her school bag?
There is no work done as the force of her bag is in a downwards direction.
60 N x 0 = 0 J
What is the Si unit for work done?
J for Joules!
Alicia kicks a ball which weighs 50 N horizontally, with a force of 60 N across the field 200 m away from her. What is the force done by Alicia to the ball
60 N x 200 m = 12000 J !!
If you used 50 N, it’s incorrect because 50 N represents the downward/ gravitational force acting on the ball.