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AP Physics 1
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Gravity
Terms in this set (41)
What two entities comprise a vector?
Magnitude and direction
What do you do with any vector that is not on either the x or y axis?
Break it up into x and y components using trig, add up the components.
How are velocity and speed different?
Velocity has a direction and speed does not have direction.
What quantity is calculated from slope of the displacement versus time graph?
velocity
What does upward slope on a displacement versus time graph imply about the velocity.
The velocity is positive
What is acceleration?
How quickly you change velocity.
What is the area under the velocity time graph?
Displacement
What is the y intercept of the velocity time graph?
The initial velocity, (Vo in the formulas)
What is the area under the acceleration versus time graph?
The CHANGE in velocity.
What is the horizontal acceleration of projectiles?
ZERO
What direction controls time in falling body and projectile motion problems?
Vertical direction
What do you know about two objects that are launched at different horizontal velocities?
They fall, vertically, the by the same amount in the same time.
What equation describes the distance that a dropped object falls "t" seconds after it started moving?
x=(1/2)at^2 Remember, the word "dropped" implies no initial velocity.
What equation describes the distance that a horizontally launched projectile falls t seconds after it started moving?
x=(1/2)at^2 ...Horizontal velocity does not affect the time of fall.
What equation describes the speed of a dropped object "t" seconds after it started moving?
V=Vo + at ...The word "dropped" means no initial velocity.
What equation describes the speed in the x-direction of a projectile "t" seconds after it started moving?
Vx=(Vxo)t ...Recall that there is no acceleration in the horizontal direction.
What equation describes the speed in the y-direction of a projectile "t" seconds after it started moving?
Vy=Vyo + gt ...Watch the signs.
What is implied when an object is not accelerating in the x direction?
The body is moving at a constant velocity
What is implied when an object is not accelerating in the y direction?
g=zero so h=(Vyo)t
When is sum of force (net force) zero.
When a body is moving at a constant velocity or not moving at all.
When is sum of force (net force) NOT zero.
When a body's speed is changing.
What force is always present, and what is its equation?
Weight ...w=mg
How is sum of force (net force) depicted in a free body diagram?
It is an arrow that DOES NOT touch the body. Recall that the net force is the answer when all the forces are added up.
When is a normal force present, what is its direction?
When the body rests on a surface.
What is the component of "mg" parallel to a slope?
(mg)sin(angle)
What is the general equation for motion down a slope and how does it change if the object is going up the slope?
x=Vo + ((1/2)g)sin(angle)t^2
In uniform circular motion, how is tangential velocity calculated?
2(pi)R/T ...Circumference/Period
What is the direction of the centripetal force?
The centripetal force points along the radius towards the center of the circle.
What is the direction of the centripetal acceleration?
The centripetal acceleration points along the radius towards the center of the circle. (Just like the centripetal force.)
How is the centripetal force represented in a free body diagram?
It is the net force pointing towards the center.
A ball rolls inside a salad bowl. The ball is released along the top edge and rolls down before climbing to the same height on the opposite side of the bowl. What is the direction of the acceleration of the ball when it at the top edge of the bowl?
It is towards the center and downwards a little. It is the sum of the normal force perpendicular to the bowl and the weight downwards.
A ball rolls inside a salad bowl. The ball is released along the top edge and rolls down before climbing to the same height on the opposite side of the bowl. What is the direction of the acceleration of the ball when it at the bottom of the bowl?
The acceleration is towards the center. It is supplied by the normal force and points towards the center.
Mathematically what does centripetal force represent and how is centripetal force calculated?
The centripetal force is the net force. It's magnitude is calculated from F=ma where "a" is the centripetal force.
How is a force's direction oriented compared to a bodies direction of motion to get a circular (curved) path of motion?
The force is perpendicular to the motion to get a circular path of motion. (Think about centripetal force.)
How much work is the work done on an object moving in a circle? Why?
Zero. Because the displacement is perpendicular to the force (centripetal force.)
If you double the mass of one planet, triple the mass of another, and move them twice as far apart, what happens to the force of attraction between them?
The new force is 2/4 or 1/2 times the old force. ...Because the force of gravity varies directly with the masses and inverse squared to the distance apart.
What is the derived equation for the ACCELERATION of gravity in terms of m and "r" squared?
G(M:earth)/r^2 ...force of gravity = G(M:earth)(M:body)/r^2
How can total momentum be calculated?
Adding the momentum of all the bodies.
What is the difference between elastic and inelastic collisions? State the relevant equations for each.
kinetic energy is conserved for an elastic collision and not for an inelastic collision. ELASTIC: m1v1 + m2v2 = m1v1'+m1v2': INELASTIC: m1v1 + m2v2 = (m1+m1)v
What is impulse?
Impulse is the change in momentum
How does impulse relate to force?
Impulse is (force)(time)
;