Answer:
A. 231.77 J
B. 5330.71 J
C. 46 donuts
Explanation:
A. To lift the barbell once, she will have to extend it the full length of her arm. The work done will then be:
W = F * d
Where the force is the weight of the barbell.
F = m * g
Hence, the work done in lifting the barbell is:
W = m * g * d
W = 43 * 9.8 * 0.55
W = 231.77 J
B. If she does 23 repetitions, the total energy she expend will be equal to the Potential energy when the barbell is lifted multiplied by 23:
E = 23 * m * g * d
E = 23 * 231.77
E = 5330.71 J
C. 1 Joule = 4.184 calories
5330.71 Joules = 5330.71 * 4.184 = 22303.69
If 1 donut contains 490 calories, the number of donuts she will need will be:
N = 22303.69/490 = 45.5 donuts or 46 donuts
I believe it is A. positive acceleration since it is speeding up
Answer : The de-Broglie wavelength of this electron, 
Explanation :
The formula used for kinetic energy is,
..........(1)
According to de-Broglie, the expression for wavelength is,
or,
...........(2)
Now put the equation (2) in equation (1), we get:
...........(3)
where,
= wavelength = ?
h = Planck's constant = 
m = mass of electron = 
K.E = kinetic energy = 
Now put all the given values in the above formula (3), we get:
conversion used : 
Therefore, the de-Broglie wavelength of this electron,
