Definitions
A vector quantity needs two things to accurately express it. What are they?
magnitude and direction
A car travels 300 m and 5 s. What is its average velocity.
60 m/s
Force is measured in what unit?
newtons
What is the name of the force that deflects straight-line motion into circular motion?
centripetal force
FINAL JEOPARDY
Vectors
A cannon ball leaves a cannon with a velocity of 40 m/s at an angle of 45o . Calculate the x and y components of its velocity.
What is displacement?
position relative to the starting point
A body falls from rest a distance of -45 m with no air resistance. What is the time of its fall ?
3 s
What does the law of balanced forces (Newton's First Law) state?
When all the forces on a free body are balanced, the object will continue it its state of motion.
What is the name of the acceleration that occurs when a body moves in a circular path?
centripetal acceleration
True or False? The amount of work needed to move a body from one height to another using a machine (pulley system or incline) can never be less than the change in the body's energy state.
True
What is the definition of work?
Work is done when a force moves a body through a distance.
A body is propelled straight up at 45 m/s. After how may seconds does it reach its maximum height, and what is its velocity at this height?
4.5 s and 0 m/s
How much force is needed to accelerate a 1 kg mass 2 m/s/s?
2 N
How does the centripetal force needed to hold a body in a circular force change when when the velocity is tripled?
It increases by a factor of nine.
When you slide a body up an inclined plane, what two forces do you do work against?
friction and gravity
What is the definition of acceleration?
The change in velocity per change in time.
What is the final velocity when a runner accelerates from rest at 2m/s/s for 3 s?
6 m/s
What is the acceleration when a 20 N force acts on a 10 kg mass?
2.0 m/s/s
What is the centripetal force needed to keep a 3 kg body circling with a radius of rotation of 1 m and a tangential speed of 2 m/s?
12 N
How much work is required to slide a 20 N body up a frictionless incline whose length is 1 m, and the angle of incline is 30o
10 N
What is the definition of a watt?
one joule per second
A body falls from rest for 6 s. Calculate the displacement during the 6 s.
180 m
The coefficient of friction between a body and a surface is 0.4. Calculate the kinetic friction force as the body is slid across the surface. The body's weight is 5 N.
2 N
True or False? If the radius of a circling body is reduce to 1/3, the centripetal force must increase by a factor of 3.
True
A body has a mass of 6 kg. What is the downward component of its WEIGHT parallel to an inclined plane with a 30o incline?
30 N