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21 terms

Formulas/Practice Problems

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Power
Force (F) x Distance (d) = Work W
Work
Power= Work ÷ Time
Acceleration
a= (velocity2-velocity1)÷ time
Velocity 2
velocity2= velocity1+ (acceleration×time)
Distance
Distance= Work÷ Force
Time (acceleration)
Time= (velocity2- velocity1)÷ acceleration
Force
Force= Work÷ distance
Work (if you have power and time)
Work=Power × time
Time (power)
time = work ÷ power
A roller coaster car rapidly picks up speed as it rolls down a slope. As it starts down the slope, its speed is 4 m/s. But 3 seconds later, at the bottom of the slope, its speed is 22 m/s. What is its average acceleration?
a= (V2-V1)÷ t
a= (22-4)÷3
A= 18÷3
A=6 m/s/s
Amy uses 20N of force to push a lawn mower 10 meters. How much work does she do?
Work= Force×distance
Work= 20 N × 10 m
Work = 200 N/m
Frank does 2400J of work in climbing a set of stairs. If he does the work in 6 seconds, what is his power output?
Power= Work ÷ time
Power= 2400 J ÷ 6 s
Power= 400 J/s
A 900N mountain climber scales a 260m cliff. How much work is done by the mountain climber?
Work= Force×distance
Work= 900 N × 260m
Work=234,000 N/m
A woman runs a kilometer using a force of 210N and a power output of 500W. How long in minutes does it take this woman to complete 1 kilometer?
Work= Force×distance
Work= 210 N × 1000m
Work= 210,000 N/m
time = work ÷ power
time= 210,000 N/m ÷ 500 W
time= 400 s
A Car accelerates from 2 m/s to 130 m/s in 12 seconds. What is the lizard's average acceleration?
a= (V2-V1)÷ t
a= (130m/s-2m/s)÷ 12s
a= 128m/s ÷ 12s
a= 10.67 m/s/s
If a Ferrari, with an initial velocity of 10 m/s, accelerates at a rate of 50 m/s/s for 3 seconds, what will its final velocity be?
velocity2= velocity1+ (acceleration×time)
V2= 10 m/s + (50 m/s/s × 3s)
V2= 10m/s+150 m/s/s
V2= 160 m/s
Josh rolled a bowling ball down a lane in 2.5 s. The ball traveled at a constant acceleration of 1.8 m/s2 down the lane and was traveling at a speed of 7.6 m/s by the time it reached the pins at the end of the lane. How fast was the ball going when it left Tim's hand?
velocity1= velocity2 - acceleration×time
A runner covers the last straight stretch of a race in 4 s. During that time, he speeds up from 5 m/s to 9 m/s. What is the runner's acceleration in this part of the race?
a= (V2-V1)÷ t
a= (9 m/s- 5 m/s)÷ 4 s
a= 4m/s ÷ 4 s
a= 1m/s/s
How much Power is required to pull a sled if you use 60J of work in 5 seconds?
Power= work ÷ time
Power= 60 J ÷ 5s
Power= 12 Watts
Intial velocity
V1= V2-at
A skateboarder executes 20 leaps across the skate park in 3 minutes. The power it takes her to do this is 12 watts with a force of 30 N. What is the total distance she travelled?
3*60= 180
Work=Power × time
Work= 12W ÷ 180s
Work=2160 J
Distance= Work÷ Force
Distance= 2160 J÷ 30 N
Distance= 72 m