P8 - FORCES IN BALANCE
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What is a scalar quantity?
A value with magnitude.
What is a vector quantity?
A value with magnitude and direction.
Give examples of scalar quantities.
Speed Distance Time Energy Mass Temperature Pressure Power
Give vector quantities.
Velocity Displacement Force Weight Acceleration Momentum
How does velocity differ from speed?
Velocity is a vector, speed is a scalar.
Should you use gravity force or weight?
WEIGHT
What are the four non contact forces?
Magnetic🧲 Electrostatic🔌 Gravitational🕳️ Nuclear☢️
What is Newton’s Third Law?
When two objects interact with each other, they exert equal and opposite forces on each other.
What is Newton’s Second Law?
F=ma The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
What is the formula of acceleration?
here: 🔼v ______ t
Define the centre of mass.
The point at which all mass seems to be concentrated.
What are the FOUR motions?
Acceleration Deceleration Constant speed Stationary🛑
What are the two methods to stabilise an object.
• Lower the centre of mass • Widen the base
Does the centre of mass always need mass? For example, a ring?💍
No.
Give contact forces.
Tension Compression Friction Air resistance Water resistance Drag Upthrust Lift Thrust Push force and Pull force
Define a contact force.
A force that acts when two objects touch each other.
Define a non contact force.
A force that acts when objects aren’t touching.
What is Newton’s First Law?
According to Newton’s First Law of motion, an object remains in the same state of motion unless a resultant force acts on it. If the resultant force on an object is zero, this means: * a stationary object stays stationary * a moving object continues to move at the same velocity (at the same speed and in the same direction)
Imagine a box being pushed along a floor at a constant speed. What are the forces?
Reaction force.⬆️ Push force.➡️ Weight.⬇️ Friction.⬅️
What are the forces acting on plane just off a runway?
⬆️Lift ⬇️Weight ⬅️Air resistance or drag forces ➡️Thrust
What is centripetal force?
The resultant force towards the centre of a circle acting on an object moving in a circular path.
What factors affect centripetal force?
• speed • radius of the bend • mass of the car
How can a student find the centre of mass?
Using a clamp stand, boss and clamp, position a card onto a clamp. Place this in front of a plumb bob, which always indicates the centre of the Earth. As a result, a student can draw lines on the card aligning with the string attached to the plumb bob. When done with a second hole, the crossing point shows the centre of mass.
How can a student check the centre of mass is accurate?
• Balancing the card on a small object like their finger • At the crossing point • Proves - if balanced - that the centre of mass is accurate.