Answer:
a. negative
b. zero
Explanation:
work is the change in the energy of a system due to external forces
work is done when a force moves a load through a distance in the direction of the force
The work done by a force on a system is positive when the force and the force displacement point in the same direction and negative when they point in opposite directions
in the scenario we are considering in the question, the force (the hand) moves the block vertically upwards but the displacement of the block reduces (in the opposite direction) since it decelerates. as such the work done by gravity on the block is negative.
the work done on the block is zero if the system consists of the block and the earth because there is no gravitational force exerted on the system
Answer:
Explanation:
We shall consider the balance of forearm . The weight is balanced by tension created in the bicep of forearm.
The weight of forearm will act downward . Let it be W. Tension T of bicep will pull the forearm upwards . Bicep muscle is attached at a point between palm and elbow. Its other end is attached with hind arm . If we hold the forearm parallel to ground , weight acts vertically downwards and tension in bicep makes some angle with the vertical . Let it be θ.
Vertical component of tension T
= T cos θ . It will balance W .
T cos θ = W
T = W / cos θ
the value of cos θ will always be less than 1.
so T > W . or
tension in bicep is more than weight of forearm.
Answer:
4.9 minutes
Explanation:
Given; T(t) = Ce^-kt + Ts
Now;
T(t) = 190 degrees Fahrenheit
Ts = 60 degrees
To obtain C;
190 = Ce^0 + 60
190 - 60 = C
C = 130
Hence, to find k when t=11
172 = 130 e^-11k + 60
172 -60/130 = e^-k
e^-k = 0.86
ln(e^-k) = ln( 0.86)
-k = -0.15
k = 0.15
Hence at 122 degrees, t is;
T(t) = Ce^-kt + Ts
122 = 130e^-0.15t + 60
122 - 60/130 = e^-0.15t
0.477 = e^-0.15t
ln (e^-0.15t) = ln (0.477)
-0.15t = -0.74
t = 0.74/0.15
t = 4.9 minutes
A=(Vo-V)/t=(10-0)/0.26=10/0.26=38.46m/s2
F=ma=70*38.46=2692.3N
Current = voltage / resistance = 120 / 24 = 5 Amperes
Voltage = current x resistance = 6 x 10 = 60 Volts
