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Speed & Velocity
Speed & Velocity II
Acceleration
Free Fall
Miscellaneous
100
What is the equation for average speed?
Distance covered divided by the time interval.
100
What is the average speed of a moth flying 20 m in 4 seconds?
20 m ÷ 4s = 5 m/s
100
How do you calculate acceleration?
Change in velocity divided by time interval.
100
Free fall is motion under the influence of what?
Gravity.
100
A car is driving at 30 m/s, and speeds up to 60 m/s. If the max acceleration of the car is 2.5 m/s2, how long does it take?
2.5 m/s2 = (60 m/s - 30 m/s) ÷ t
t = 12 s
200
What type of speed tells you how fast you are going at one specific moment?
Instantaneous speed.
200
How far will a rocket travel in 10 seconds if it has a speed of 250 m/s?
250 m/s × 10 s = 2,500 m or 2.5 km.
200
The acceleration of gravity is always in what direction?
Down
200
If an apple falling out of a tall tree hits the ground 2.0 s after it falls, how fast is it going when it hits?
vf = at
vf = 9.8 m/s2 × 2.0 s = 19.8 m/s
(or about 20 m/s)
200
If you throw a ball straight up in the air at 10 m/s what will be the ball's speed when you catch it?
10 m/s
300
Velocity includes speed and what other value?
The direction.
300
How long will it take a Nolan Ryan fastball to reach home plate, if he can pitch at 48 m/s and it is 18.4 m from the pitcher's mound?
18.4 m &divide 48 m/s = 0.38 s.
300
If an object is accelerating, what is true about the distance it moves each second?
It increases.
300
A boy is bouncing on a trampoline. If the trampoline allows him to jump with an initial upward speed of 8.5 m/s, how long is he in the air?
vf = v0 + at
0 = 8.5 m/s + 9.8 m/s2 x t
t = 1.73 s
300
If a ball is thrown straight up at 10 m/s, how high will it go?
vf2 = v02 + 2ad
(10 m/s)2 = (0 m/s)2 + 2 x (-9.8 m/s2) x d
d = 5.10 m
400
Is it possible to have a constant speed without a constant velocity?
Yes, you can change direction.
400
It is 2 minutes until class begins, and a student in Ms. Bowen's class needs to stop by his locker to get his book before class. If he has a total of 96 m to travel, at a walking speed of 1.2 m/s, how much time can he spend at his locker?
Walking time = 96 m &divide 1.2 m/s = 80 s.
120 s - 80 s = 40 s.
400
What is the acceleration of a cannonball that is fired at 200 m/s in a time of 0.1 s?
200 m/s ÷ 0.1 s = 2,000 m/s2
400
How far does a rock fall in 3.5 s?
df = ½ at2
df = 4.9 m/s2 × (3.5 s)2
df = 60 m
400
What is the acceleration on a penny dropped from the top of the Empire State building which is 381 m high?
9.8 m/s2
500
If you travel 9 km in 2 hours, what is your instantaneous speed?
It is unknown, since you can only calculate the average speed of 4.5 km/h.
500
How many seconds will it take a jumbo jet to travel 720 m if it is flying at 100 m/s?
t = 720 m ÷ 100 m/s = 7.2 s
500
What acceleration is required to slow a car from 85 m/s to 40 m/s in 2.5 s?
(40 m/s - 85 m/s) ÷ 2.5 s = -18 m/s2
500
A helicopter suddenly loses power and needs to be restarted while it is flying. If the helicopter takes 12 s to restart, and it was 700 m above the ground when it lost power, will it crash?
Yes. It will fall over 700 m in 12 seconds.
500
If you were on Mars and saw that if you dropped a hammer from 0.90 m, and it hit the ground after 0.68 s, what would you calculate for the gravitational acceleration (g) on Mars?
df =1/2a × t2
.90m = 1/2 × a × (0.4624 s)2
a = 3.9 m/s2