Science

SCIENCE NOTES (sorry the pictures didn't come through)

Zoey Poll

Newton’s Laws of Motion

The law of inertia:
Every object continues in a state of rest or of uniform speed in a straight line unless acted on by a nonzero (or unbalanced) force.


Examples:
• A sheet of paper can be quickly withdrawn from under a soft drink can without the can toppling, because the can has inertia.
• If you swing a stone overhead in a horizontal circle and the string breaks, the tendency of the stone is to follow a straight-line path.

The law of acceleration:
The acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object.
• Fforce)=m(mass)a(acceleration)
Equation for acceleration:
Acceleration = net force/mass
A = F/m

Small net force, large mass ⇒small acceleration
Large net force, small mass ⇒ large acceleration


Examples:
• Consider a cart pushed along a track with a certain force. If the force remains the same while the mass of the cart decreases to half, the acceleration of the cart doubles.
• Push a cart along a track so twice as much net force acts upon it. If the acceleration remains the same, what is a reasonable explanation? The mass of the cart doubled when the force doubled.

When acceleration is g – free fall.
When the only force acting on a falling object is gravity, with negligible air resistance, the object is in free fall. An object in free fall accelerates toward Earth at 10 m/s per second.

Examples:
• At one instant an object in free fall has a speed of 40 m/s. Its speed one second later is 50 m/s. (We assume the object is falling downward.)

Twice the force on twice the mass → same acceleration as half the force on half the mass.

Examples:
• A 5-kg iron ball and a 10-kg iron ball are dropped from rest. For negligible air resistance, the acceleration of the heavier ball will be the same.
• A 5-kg iron ball and a 10-kg iron ball are dropped from rest. When the free-falling 5-kg ball reaches a speed of 10 m/s, the speed of the free-falling 10-kg ball is 10 m/s.
When acceleration is g—free fall.
The ratio of weight to mass is the same for all falling objects in the same locality; hence, their accelerations are the same in the absence of air resistance.


Examples:
• Demonstration of a feather and a coin in a vacuum. In a vacuum, a feather and a coin fall together at g—the acceleration due to gravity.
• When an air filled glass tube containing a coin and a feather is inverted, the coin falls quickly to the bottom of the tube while the feather flutters to the bottom.