Types of Motion
What are the three types of motion?
At Rest, Constant Speed, Acceleration
A car is moving with a constant speed of 30 meters per second. What is its average speed after 40 seconds of motion?
30 m/s
A car begins at rest and accelerates. What is the initial speed of the car?
A boat is travelling at 20 meters per second and accelerates to 46 meters per second. What is the average speed of the boat?
vavg = (vi+vf) / 2
vavg = (20 m/s + 46 m/s) / 2
vavg = 33 m/s
Objects fall freely because of what force?
Gravity
You are sitting at your desk. What type of motion is this?
At rest
A cyclist rides 4000 meters in 3 minutes. What is the average speed of the cyclist?
vavg = d/t
vavg = (4000 m) / 180 s
vavg = 22.2 m/s
A bus slows down as it approaches a stop sign. What is the final speed of the bus?
vf = 0 m/s
A boat accelerates from 20 meters per second to 46 meters per second. If this takes 120 seconds, what is the acceleration of the boat?
a = (vf - vi) / t
a = (46 m/s - 20 m/s) / 120s
a = 0.217 m/s
As an object falls towards the ground, what happens to its speed?
It increases.
A ball is rolling down a ramp. What state of motion is this?
Acceleration
A car moves at an average speed of 30 meters per second for 20 minutes. How far did the car travel?
vavg = d/t
30 m/s = d/(1200s)
d = 36000 m
A horse is speeding up as it trots down the path. How does the initial speed compare to the final speed?
vi < vf
A boat at rest accelerates at a rate of 0.75 meters per second squared for 30 seconds. What is the final speed of the boat?
a = (vf - vi)/t
0.75 m/s2 = (vf - 0 m/s)/30s
vf = 22.5 m/s
As an object falls towards the ground, what happens to its acceleration?
It remains the same, 9.81 m/s2.
What is the difference between instantaneous speed and average speed?
Average speed is a measurement over time that summarizes the speed of an object. Instantaneous speed is an object's speed in a specific moment.
A boat is moving at a constant speed of 15 meters per second. How long does it take for the boat to travel 1000 meters?
vavg = d/t
15 m/s = (1000 m)/t
d = 66.7 seconds
A car is in cruise control on the highway. How does the initial speed compare to the final speed?
vi = vf
A bus accelerates from 15 meters per second to 30 meters per second over 400 seconds. How far did the bus travel in this time? (Hint: You may need to do two calculations)
vavg = (vi + vf) / 2
vavg = (15 m/s + 30 m/s) / 2
vavg = 22.5 m/s
vavg = d/t
22.5 m/s = d/400s
d = 9000 m
An object on Earth is dropped. It takes 20 seconds to fall. From what height was the object dropped?
d = vit + 1/2at2
d = (0) + 1/2(9.81 m/s2)(20 s)2
d = 1962 m
A car has zero acceleration. What is/are the possible state(s) of motion of the car?
Saturn orbits the sun at an average speed of 403 meters per second. It travels 374,515,315,200 meters during this orbit. How long does it take Saturn to orbit the Sun in years?
vavg = d/t
403 m/s = (374,515,315,200 m)/t
t = 929,318,400 s
years = 929,318,400 s / 60 s in a min / 60 min in an hr / 24 hrs in a day / 365 days in a yr
t = 29.5 years
A jogger is running at a constant speed. How does her average speed change over time?
It remains the same
A car accelerates from a speed of 10 meters per second. It takes 40 seconds for the car to accelerate, and in this time, the car travelled 450 meters. What is the acceleration of the car?
d = vit + 1/2at2
450 m = (10 m/s)(40 s) + 1/2a(40 s)2
450 = 400 + 800a
50 = 800a
a = 0.0625 m/s2
An object on Earth is dropped from a height of 350 meters, how long does it take for the object to fall?
d = vit + 1/2at2
350 m = (0) + 1/2(9.81 m/s2)t2
350 m = (4.905)t2
71.356 = t2
t = 8.45 s