Back to the Basics
What is accuracy?
How close a measurement is to the actual (true) value
A small cart has a velocity of -5 m/s. It has an acceleration on -1 m/s^2. What is happening to the speed of the cart?
It is speeding up (in the negative direction)
A bowling ball and a flat piece of paper are dropped from the same height in this classroom. Which will hit the ground first? Why?
Bowling ball.
The paper has more air resistance
Which object has the greatest inertia?
a) A 10 lb dumbbell
b) A 25 lb plate
c) A 45 lb bar
c) A 45 lb bar
A box slides down a ramp. What type of work is done by:
a) Gravitational force
b) Normal force
c) Friction force
a) positive
b) zero
c) negative
Draw a target with three arrows on it that demonstrates high accuracy but low precision.
A cart has an acceleration of 0 for three seconds. What must be true about the velocity of the cart in that time?
The velocity is constant (not changing)
What is the vertical velocity of a projectile at the top of its motion?
0
The net force acting on a book is to the left. In what direction is the book accelerating?
To the left
A leaf falls from a tree. Is mechanical energy conserved in this situation? Why or why not?
Yes, energy is transformed from gravitational potential energy (GPE) to kinetic energy (KE). Also, there are no external forces acting on the system.
Identify the number of significant figures in:
a) 10,050
b) 0.002501
c) 10.250
a) 4
b) 4
c) 5
A small cart has a velocity of 8 m/s. It has an acceleration on -2 m/s^2. What is happening to the speed of the cart for the next three seconds?
It is slowing down
What is the vertical acceleration of a projectile at the top of its motion?
-9.8 m/s^2
A 10 kg block is being pushed across a frictionless surface. The block is accelerating at 1 m/s^2. The force acting on the block is doubled. Now what is the acceleration of the block?
2 m/s^2
A block slides to a stop on a surface. Is mechanical energy conserved in this situation? Why or why not?
No, energy is lost (converted to thermal energy) by friction
Round each number to 3 significant digits.
a) 5.4991
b) 0.002617
a) 5.50
b) 0.00262
A cart has a velocity of 0 for three seconds. What must be true about the motion of the cart in this time?
What is the horizontal velocity of a projectile at the top of its motion?
The same as its initial horizontal velocity
A wooden block sliding across a flat surface is in equilibrium. What must be true about:
a) its velocity?
b) its acceleration?
c) the net force acting on it?
Velocity: constant
Acceleration: 0
Net force: 0
Student A completes 100 J of work in 10 s.
Student B completes 100 J of work in 15 s.
Student C completes 75 J of work in 15 s.
Order the students from least to greatest power delivered.
Least -> C, B, A <- Greatest
Convert 15 m/s to km/hr.
54 km/hr
What is the fundamental cause of the acceleration of an object?
An unbalanced net force
What is the horizontal acceleration of a projectile at the top of its motion?
A box is falling through the air while being blown to the right by an extremely strong fan. What direction would someone need to push (or pull) the box in order to keep it from moving? Draw a free body diagram for this situation.
Up and to the left
See board.
Draw energy charts for:
Two students are playing catch on the bleachers. The student will the ball is at the bottom of the bleachers. The student waiting to catch the ball is at the top.
System: Earth and Ball
Initial state: The ball has just been tossed up into the air from the ground
Final state: The ball is about to be caught
See board.