How Is Work and Kinetic Energy Calculated in Physics Problems?

AI Thread Summary
The discussion focuses on calculating work and kinetic energy in various physics problems. A 2.5-kg book falling from a height of 3.0m involves gravitational work, while a hydraulic lift must perform a specific amount of work to raise a 150-kg block. The kinetic energy of a roller coaster car at the bottom of a 50m hill is derived from potential energy conversion, with calculations leading to options G or H. Additionally, the kinetic energy of a paint chip from a satellite is evaluated, with potential answers being A or B. Lastly, the final speed of an automobile after acceleration is calculated, with the answer being option J.
Junebugg
Messages
1
Reaction score
0

Homework Statement



6. A 2.5-kg book slides horizontally and falls from a shelf 3.0m above the floor. How much work does the force of gravity do on the book as it falls 3.0m?
F. 1.2 J
G. 7.5 J
H. 24.5 J
J. 73.5 J

7. Which of the following is the minimum amount of work done by a hydraulic lift to raise a 150-kg aluminum block 2.0m vertically?
A. 75 J
B. 300 J
C. 1470 J
D. 2940 J

8. The motion of roller coasters depends upon the conversion of potential and kinetic energy. a 100-kg car starts from rest at the top of a hill with a height of 50 m. Which of the following is this car's kinetic energy at the bottom of the hill?
F. 150 J
G. 5000 J
H. 49,000 J
J. 98,000 J

9. A 0.25-g paint chip comes off a satellite orbiting Earth. The velocity of the paint chip is 7000 m/s. Which is the kinetic energy of the paint chip?
A. 1750 J
B. 6125 J
C. 12,250 J
D. 24,500 J

10. An automobile was moving at 15 m/s and accelerated at 2 m/s^2 for 2 s. Which was its final speed?
F. 17 M/S
G. 25 M/S
H. 27 M/S
J. 35 M/S

Homework Equations


ke=1/2mv^2



The Attempt at a Solution


for 8 I'm getting G or H
for 9 I'm getting A or B
for 10 I'm getting J
 
Physics news on Phys.org
Pls post your working.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top