Motion & Forces 2019

Motion & Forces 2019 Calculations Practice: Name Period Key Speed = Distance/time Velocity = Displacement/time (direction) Acceleration = (vf-vi)/time Force = mass x acceleration Weight = mass x gravity Momentum (p) = mass x velocity 1. What is the difference between distance and displacement? Draw a picture if necessary. distance-scalar-how far an object has travelled displacement-vector-how far an object has moved from its starting point 2. If I go 3 miles east, 5 miles south, and 3 miles west, what are my displacement and distance?   3 mi distance Il mi displacement=5 mi south \[3m_{1}\] 5 mi 3. Convert 4 days to seconds. (4d measure) 24hr 36005 = 345,600 300,0005 4 days 24hr today Times hr 4. If a train goes 52 mi/hr for 2 days, how far will it go? 2500MI \[S=\frac{d}{t}\] 2000 m. 52 mi/hr 48hr 2496 mi 5. If a sprinter goes from 0 m/s to 8 m/s in 0.1 seconds, what is her acceleration? \[a=\frac{v_{f}-v_{i}}{t}\] 8m/s 0m/s = $ \(80~m/s^{a.}\) 6. If you shout into the Grand Canyon, your voice travels at the speed of sound \((340~m/s)\) the bottom of the canyon and back, and you hear an echo. How deep the Grand Canyon at a spot where you can hear your echo 5.2 seconds after you shout? \[340~m/s=\frac{2d}{5.2s}\] \(d=884\rightarrow\) BB0 м \[5=390m/s\] \[t=5.2\] \[(340)(5.2)=2d\] \[x=:2d\] 7. objects drop with an average acceleration of \(9.8~m/s^{2}.\) If an object falls long will it take before it reaches a speed of \(49~m/s?\) \[\alpha=9.8m/s^{2}t=?\] \[.8m/s^{2}=\frac{49-0}{t}=\boxed{5.0s}\] \[v_{+}=49~m/s\] \[v_{m}=2~m/s\] 8. weight (in pounds) of a 7.0 kg bowling ball on Earth's surface. \((1kg=\) 2.2 lbs) What is the weight in N? \[N=mg\] 7.0 kg 2.216 15 lbs \[5).71kg\] \[(7.0kg)(9.8)=68.6\rightarrow\boxed{69~N}\] 9. What is the mass of a 7.0 kg bowling-ball on the surface of the moon? 7.0 kg anywhere! 10. What is the weight (in Newtons) of a 7.0 kg bowling ball on the surface of the moon? (Gravity on the moon is 1.6 m/s²) Wmoon = mg Wmoon = (7.0 kg)(1.6 m/s²) = 11 N 11. Would a balance function correctly on the moon? Why or why not? Yes. The unknown masses would tip the scale 1/6 12. What is the rate of acceleration of a 2,000-kilogram truck if a force of 4,200 N is used to make it start moving forward?   F = ma 4200 N = (2000 kg)(a) a = 2 m/s² 13. How much force is needed to accelerate a 68 kg skier at a rate of 1.2 m/s²? F = ma F = (68 kg)(1.2 m/s²) = 81.6 N 14. What is the mass of an object that needs a force of 4,500 N to accelerate it at a rate of 5 m/s²? F = ma 4500 N = (m)(5 m/s²) m = 900 kg 15. My friend's mass is 65 kg. What is her weight in N? W = mg W = (65 kg)(9.8) = 637 N 16. Calculate the momentum of a 11.35 kg wagon rolling down a hill at 12 m/s. p = mv p = (11.35 kg)(12 m/s) = 136.2 kg*m/s 17. Which has more momentum: a 6,000 kg elephant napping or a 0.15 kg baseball traveling at 40 m/s? p = mv p = (6000 kg)(0 m/s) = 0 kg*m/s p = (0.15 kg)(40 m/s) = 6 kg*m/s 18. Which has more momentum: a 111 kg linebacker running at a speed of 5.6 m/s or a 82 kg quarterback moving at 2.5 m/s? p = (111 kg)(5.6 m/s) = 620 kg*m/s p = (82 kg)(2.5 m/s) = 205 kg*m/s