Calculating velocity in regards to the mass and kinetic energy of an object

AI Thread Summary
To calculate the velocity of a baseball with a mass of 145 g and 94 J of kinetic energy, the correct mass in kilograms is 0.145 kg, not 0.0145 kg. The formula used is v = √(2Ek/m), which leads to the calculation v = √(2 * 94 J / 0.145 kg). This results in a velocity of approximately 36 m/s, aligning with the book's answer. The confusion arose from using the incorrect mass value in the calculation.
v3ra
Messages
21
Reaction score
0

Homework Statement



How fast is a baseball with a mass of 145 g traveling if it has 94 J of kinetic energy?

Homework Equations



m = 145 g or 0.0145 kg
Ek = 94 J
v = ?

v = √2Ek/m

The Attempt at a Solution



I get...
v = √2(94)/0.0145 kg
v = √12966
v = 114

But my book says it should be 36 m/s. What am I doing wrong?

It also mentions that I need to recall that 1 J = 1 kg . m^2/s^2 but I am unsure how to incorporate this into the equation or if it is even necessary.
 
Physics news on Phys.org
Your mass should be .145 kg.
 
Your mass should be 0.145 kg and not 0.0145kg
 
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