kinematics and statics
what's the difference between speed and velocity
speed is a scalar and velocity is a vector
in which type of collision is kinetic energy conserved
elastic collisions
a ball rolls down a hill with friction. is energy conserved?
Units for energy
Joules (J)
what does the slope of a position-time graph represent
velocity
A moving object collides with a stationary object. Is it possible for both objects to be at rest after the collision?
No, because of conservation of momentum. if the moving object stops, the stationary object must be moving to conserve momentum
a particle has mass m and moves with speed 2v. a second particle has mass 2m and moves with speed v. which has the higher KE?
the first particle
units for work
Nm
What factors affect torque?
Magnitude of force
distance from pivot
angle between force and lever arm
Tao=rFsintheta
do momentum and angular momentum change in circular motion
a ball rolls down a hill with friction. what type of kinetic energy allows it to make distance?
KE_t
Units for momentum
kg*m/s
what's the difference between centripetal and tangential acceleration
centripetal changes direction of velocity without affecting its magnitude. tangential changes the magnitude of the velocity without the direction
a one million pound truck hits me in the school parking lot. which one of us experiences the greater change in momentum?
we experience the same change in momentum
you have 2 springs with different spring constants. If both springs are stretched by the same force, which spring has more work done on it?
the one with a lower spring constant. higher k = stiffer spring = less distance stretched. W=F*d
Newtons fundamental unit
kg*m/s
Three projectiles are launched at the same speed at different angles
1: 30 degrees
2. 45 degrees
3. 60 degrees
rank them based on the horizontal distance they cover
1=3<2
for 1 and 3, angles adding up to 90 degrees yield the same horizontal distance
45 degrees is the angle that yields the farthest horizontal distance
R=[(v^2)sin(2theta)]/g
explain how seatbelts/airbags work using force and impulse
f(avg) = J/t
change in momentum is constant. increasing change in time of the impact decreases the force of the impact
A crate is pulled up 6m up an incline with a force of 50N. If U increases by 250J, what work is done by friction?
W=F*d= 50N * 6m = 300Nm
W_friction = 300J-250J= 50J
hannahs favorite units
(in fundamental units)
W = J/s = kg*m2*s-3