Waiting in line at the DMV
What is the formula for density?
D = M/V
What is speed?
The change in distance over time. (How fast something is going)
What graph do we use to determine speed?
distance vs time graph
What is acceleration?
The change in velocity over time (rate of change of velocity). How quickly an object is speeding up or slowing down.
True or false: speed is a scalar quantity, velocity is a vector quantity
True
What is density?
The amount of mass in a certain volume. Describes how tightly packed the molecules of an object are.
What is the difference between speed and velocity?
Speed measures change in distance over time, velocity is speed and the direction of motion.
Speed is the ____ of the line on a distance vs time graph
slope
When is acceleration = 0?
When the object is moving at constant speed or at rest.
What is the difference between mass and weight?
Mass is how much matter an object contains (stays constant), weight is dependent on downward pull on an object due to gravity (changes depending what planet you are on!)
How do you calculate mass, given density and volume?
Mass = density * volume
What is the difference between distance and displacement?
Distance is how far an object traveled in total, displacement is the distance and direction of an object in relation to the reference point.
In the graph on the board, what is the speed of the object (include units!)
5/3 m/s
What is the formula and what are the units of acceleration?
A= vf-vi/t
m/s^2
What happens to the density of a gas if it is compressed into a canister?
I have an object with a density of 1.2 g/mL. What will happen to the object if I drop it in water?
It will sink
Calculator time! Usain Bolt ran the 100 meter dash in 9.58 seconds. What was his average speed? Round to the nearest hundredth and remember to include units!
10.44 m/s
In the graph on the board, what is the speed of the object (include units)!
-1/4 m/s
Calculator time! A quarterback throws a football at 25 m/s. The wide receiver catches the football (stopping the football's flight) after 5 seconds. What is the acceleration of the football? Include units!
0-25/5 = -5 m/s^2
What are some potential sources of human error when measuring density (remember density calculation includes mass and volume)?
- reading the graduated cylinder from the wrong angle
- not fully fitting the object in the graduated cylinder
- not zeroing the scale before using it
- having another object or liquid on the scale
Calculator time! I have 5 kilograms of chocolate with a density of 1.25 g/cm^3. What volume of chocolate do I have? You only get the points if you include units!
4,000 cm^3
Calculator time! I am driving a car at 55 miles per hour. How far did I go in 11 minutes? Round to the nearest hundredth and include units!
10.08 miles (10 1/12)
A
B
C
D
A: Moving at constant speed (3 m/s) forward
B: Stopped (standing still 0 m/s)
C: Moving at constant speed (1 m/s) forward
D: Moving at constant speed (-8/3 m/s) backward
Calculator time! A person skydiving jumps out of an airplane. The acceleration due to gravity is 9.8 m/s^2. When the person reaches terminal velocity (their maximum velocity when falling), they are falling at a velocity of 200 km/hr (56 m/s). Calculate how long it takes for the skydiver to reach terminal velocity. Include units and round to the nearest tenth!
9.8 m/s^2 = 56-0/t
t= 5.7 seconds
What are some sources of precision error (measurement error) when calculating density?
- scales only measure to tenth of a gram
- graduated cylinders only measure in 1 ml increments