Review Sheet for Test Name ____________________
Speed, Velocity, Momentum, Conservation, Inertia, and Impulse favorite pie ______
Useful formulae: v = d/t p = mv ptotal before = ptotal after
100 cm = 1 m 1000 m = 1 km pa + pb (before) = p’a + p’b (after)
Part I Conversions:
a. 3.2 m = ______320____ cm b. 75 cm = __0.75______ m c. 120 kg = __120,000___ g
Part II Vocabulary -- True or False? For all False answers, fix it so that it becomes true
a. T/F Speed gives the answer to “how fast” TRUE
b. T/F Velocity includes how fast and what direction TRUE
c. T/F Momentum equals distance divided by time FALSE p=mv
d. T/F Momentum is only conserved sometimes FALSE IT IS ALWAYS CONSERVED
e. T/F There are 1000 mm in a meter TRUE
f. T/F More mass means more inertia TRUE
g. T/F It takes 50 seconds for a car to travel a distance of 1500 m at a speed of 30 m/s T
h. T/F Objects at rest will stay at rest until a force gives it momentum TRUE
i. T/F Objects in motion will eventually stop because of inertia FALSE, MOTION WON’T CHANGE UNLES WE APPLY A FORCE THAT STOPS THE OBJECT.
j. Which of these quantities are velocities? (circle each one that is a velocity)
i. 45 mph North ii. 3.8 m/s X iii. 24 miles/year downward iv. +25 m/s upward
ALL ARE EXCEPT FOR ii. VELOCITY HAS SPEED AND DIRECTION
Part III Problems
YOU MUST SHOW ALL YOUR WORK Showing work includes:
writing down the givens showing what you need to get showing the formula and units in your answer
a. Linda runs a distance of 350 meters East in a time of 70 seconds. Find her velocity.
D = 350 M T = 70 S V = ? V = D/T = 350 m / 70 s v = 5 m/s
b. A car is moving at 35 m/s. It travels 1050 meters. How much time will it take?
D = 1050 m v = 35 m/s t = ? t = d/v = 1050 m / 35 m/s = 30 s
c. Find the momentum of a boy with a mass of 72 kg running at a velocity of +7 m/s.
m = 72 kg v = +7 m/s p = ? p = mv = 72 kg (+7 m/s) = 504 kg m/s
d. A basketball player has a mass of 90 kg. She is running and has a momentum of
+540 kg m/s. Find her velocity. m = 90 kg p = +540 kg m/s v = ?
v = p/m v = +540 kg m/s / 90 kg = 6 m/s
e. A 80 kg man moving at 10 m/s crashes into a 120 kg man that had been at rest. Immediately after the perfectly inelastic collision, the men stick together and move off.
Find their velocity after the collision. (hint steps: find p before, p after, v they need to have that p)
m of first guy is 80 kg v=10 m/s other guy’s m=120 kg, v = 0 (before)
p of 1st man = 80 kg (10 m/s) = 800 kg m/s other guy has no p, so total before = 800 kg m/s
p after must also be 800 kg m/s because of conservation need to find THEIR v using v =p/m
so m of them together is 80 kg + 120 kg = 200 kg.
vtogether = p total / m total = +800kg m/s /200kg = 4 m/s
f. Conservation Problems: solve for the missing momentum! (hint: total p stays constant)
BEFORE AFTER
i. A has 65 kg m/s B has 12 kg m/s A has 30 kg m/s B 47 kg m/s
ii. A has 300 kg m/s B has 300 kg m/s A has 150 kg m/s B 450 kg m/s
Part IV Questions:
a. In a collision, two cars have different masses. The small car is going faster than the big one. If we make their speeds just right, we can get the two cars to stop after the collision. How much momentum is there after the collision? ___if they stop, p = 0_____
If momentum is always conserved, what can we say about the total amount of motion before the collision? If total before = 0, then total after also = 0_ Does the direction of the cars really matter? _YES__ Explain how this collision shows it _____
Even though both objects were moving and had momentum, the total was ZERO because the two cars had equal momentums but in the opposite directions. This only works if they are going in the exact opposite direction from each other.
b. Which has more inertia, a dump truck full of rocks or an angry deer? Explain.
Dump truck, because it has much more mass, and mass tells us how much inertia it has
c. To change the momentum of an object, you have to apply a force for some time. If you had to catch a fast baseball, why would it be important to keep your hands soft and move with the ball?
Soft hands make the ball stop more gradually. More time, less F applied (easy way)
d. Describe an experiment that would test the following hypothesis: “The more expensive my sneakers are, the faster I can run.”
Run an experiment changing the cost $$ of sneakers, and measures speed.
Part IV. MCAS Multiple Choice Questions, taken from exams from the past
For the problem above, Explain your reasoning and Show your work: B is correct
p total before = +30 kg m/s + (-15 kg m/s) = +15 kg m/s which is same as p total afterwards
m total when they stick together = 20 kg, so v = p/m = +15 kg m/s / 20 kg = +0.75 m/s right
For the problem above, Explain your reasoning and Show your work:
Do the math, and deer has the most, at 60 kg (16.4 m/s) = 984 kg m/s
For the problem above, Explain your reasoning and Show your work:
The one with the biggest mass will have the largest momentum, since v’s are all the same
FOR THE OPEN RESPONSE QUESTION, PLEASE WRITE YOUR RESPONSE ON A PIECE OF WHITE LINED PAPER. SHOW ALL WORK CLEARLY, AND USE THE BEST WRITING THAT YOU CAN. MAKE SURE TO TRY TO ANSWER ALL OF THE PARTS OF THE PROBLEM
a. p red = 0.02 kg X 2 m/s = 0.4 kg m/s p yellow = 0
b. since p total before = 0.4 kg m/s, after is SAME. Red = 0 so yellow must have 0.4 kg m/s
c. If red’s v before doubles, so does its p, and p total, so yellow will also have to be doubled
d. If red had more mass, yellow would go faster
Speed, Velocity, Momentum, Conservation, Inertia, and Impulse favorite pie ______
Useful formulae: v = d/t p = mv ptotal before = ptotal after
100 cm = 1 m 1000 m = 1 km pa + pb (before) = p’a + p’b (after)
Part I Conversions:
a. 3.2 m = ______320____ cm b. 75 cm = __0.75______ m c. 120 kg = __120,000___ g
Part II Vocabulary -- True or False? For all False answers, fix it so that it becomes true
a. T/F Speed gives the answer to “how fast” TRUE
b. T/F Velocity includes how fast and what direction TRUE
c. T/F Momentum equals distance divided by time FALSE p=mv
d. T/F Momentum is only conserved sometimes FALSE IT IS ALWAYS CONSERVED
e. T/F There are 1000 mm in a meter TRUE
f. T/F More mass means more inertia TRUE
g. T/F It takes 50 seconds for a car to travel a distance of 1500 m at a speed of 30 m/s T
h. T/F Objects at rest will stay at rest until a force gives it momentum TRUE
i. T/F Objects in motion will eventually stop because of inertia FALSE, MOTION WON’T CHANGE UNLES WE APPLY A FORCE THAT STOPS THE OBJECT.
j. Which of these quantities are velocities? (circle each one that is a velocity)
i. 45 mph North ii. 3.8 m/s X iii. 24 miles/year downward iv. +25 m/s upward
ALL ARE EXCEPT FOR ii. VELOCITY HAS SPEED AND DIRECTION
Part III Problems
YOU MUST SHOW ALL YOUR WORK Showing work includes:
writing down the givens showing what you need to get showing the formula and units in your answer
a. Linda runs a distance of 350 meters East in a time of 70 seconds. Find her velocity.
D = 350 M T = 70 S V = ? V = D/T = 350 m / 70 s v = 5 m/s
b. A car is moving at 35 m/s. It travels 1050 meters. How much time will it take?
D = 1050 m v = 35 m/s t = ? t = d/v = 1050 m / 35 m/s = 30 s
c. Find the momentum of a boy with a mass of 72 kg running at a velocity of +7 m/s.
m = 72 kg v = +7 m/s p = ? p = mv = 72 kg (+7 m/s) = 504 kg m/s
d. A basketball player has a mass of 90 kg. She is running and has a momentum of
+540 kg m/s. Find her velocity. m = 90 kg p = +540 kg m/s v = ?
v = p/m v = +540 kg m/s / 90 kg = 6 m/s
e. A 80 kg man moving at 10 m/s crashes into a 120 kg man that had been at rest. Immediately after the perfectly inelastic collision, the men stick together and move off.
Find their velocity after the collision. (hint steps: find p before, p after, v they need to have that p)
m of first guy is 80 kg v=10 m/s other guy’s m=120 kg, v = 0 (before)
p of 1st man = 80 kg (10 m/s) = 800 kg m/s other guy has no p, so total before = 800 kg m/s
p after must also be 800 kg m/s because of conservation need to find THEIR v using v =p/m
so m of them together is 80 kg + 120 kg = 200 kg.
vtogether = p total / m total = +800kg m/s /200kg = 4 m/s
f. Conservation Problems: solve for the missing momentum! (hint: total p stays constant)
BEFORE AFTER
i. A has 65 kg m/s B has 12 kg m/s A has 30 kg m/s B 47 kg m/s
ii. A has 300 kg m/s B has 300 kg m/s A has 150 kg m/s B 450 kg m/s
Part IV Questions:
a. In a collision, two cars have different masses. The small car is going faster than the big one. If we make their speeds just right, we can get the two cars to stop after the collision. How much momentum is there after the collision? ___if they stop, p = 0_____
If momentum is always conserved, what can we say about the total amount of motion before the collision? If total before = 0, then total after also = 0_ Does the direction of the cars really matter? _YES__ Explain how this collision shows it _____
Even though both objects were moving and had momentum, the total was ZERO because the two cars had equal momentums but in the opposite directions. This only works if they are going in the exact opposite direction from each other.
b. Which has more inertia, a dump truck full of rocks or an angry deer? Explain.
Dump truck, because it has much more mass, and mass tells us how much inertia it has
c. To change the momentum of an object, you have to apply a force for some time. If you had to catch a fast baseball, why would it be important to keep your hands soft and move with the ball?
Soft hands make the ball stop more gradually. More time, less F applied (easy way)
d. Describe an experiment that would test the following hypothesis: “The more expensive my sneakers are, the faster I can run.”
Run an experiment changing the cost $$ of sneakers, and measures speed.
Part IV. MCAS Multiple Choice Questions, taken from exams from the past
For the problem above, Explain your reasoning and Show your work: B is correct
p total before = +30 kg m/s + (-15 kg m/s) = +15 kg m/s which is same as p total afterwards
m total when they stick together = 20 kg, so v = p/m = +15 kg m/s / 20 kg = +0.75 m/s right
For the problem above, Explain your reasoning and Show your work:
Do the math, and deer has the most, at 60 kg (16.4 m/s) = 984 kg m/s
For the problem above, Explain your reasoning and Show your work:
The one with the biggest mass will have the largest momentum, since v’s are all the same
FOR THE OPEN RESPONSE QUESTION, PLEASE WRITE YOUR RESPONSE ON A PIECE OF WHITE LINED PAPER. SHOW ALL WORK CLEARLY, AND USE THE BEST WRITING THAT YOU CAN. MAKE SURE TO TRY TO ANSWER ALL OF THE PARTS OF THE PROBLEM
a. p red = 0.02 kg X 2 m/s = 0.4 kg m/s p yellow = 0
b. since p total before = 0.4 kg m/s, after is SAME. Red = 0 so yellow must have 0.4 kg m/s
c. If red’s v before doubles, so does its p, and p total, so yellow will also have to be doubled
d. If red had more mass, yellow would go faster