Answer:
a) F = 2250 Ib
b) F = 550 Ib
c) new max force ( F newmax ) = 2850 Ib
Explanation:
A) The force the wall of the elevator shaft exert on the motor if the elevator starts from rest and goes up
max capacity of elevator = 24000 Ibs
counterweight = 1000 Ibs
To calculate the force (F) :
we first calculate the Tension using this relationship
Counterweight (1000) - T = ( 1000 / g ) ( g/4 )
Hence T = 750 Ib
next determine F
750 + F - 2400 = 2400 / 4
hence F = 2250 Ib
B ) calculate Tension first
T - 1000 = ( 1000/g ) ( g/4)
T = 1250 Ib
F = 2400 -1250 - 2400/ 4
F = 550 Ib
C ) determine design limit
Max = 2400 * 1.2 = 2880 Ib
750 + new force - 2880 = 2880 / 4
new max force ( F newmax ) = 2850 Ib
We want to find how much momentum the dumbbell has at the moment it strikes the floor. Let's use this kinematics equation:
Vf² = Vi² + 2ad
Vf is the final velocity of the dumbbell, Vi is its initial velocity, a is its acceleration, and d is the height of its fall.
Given values:
Vi = 0m/s (dumbbell starts falling from rest)
a = 10m/s² (we'll treat downward motion as positive, this doesn't affect the result as long as we keep this in mind)
d = 80×10⁻²m
Plug in the values and solve for Vf:
Vf² = 2(10)(80×10⁻²)
Vf = ±4m/s
Reject the negative root.
Vf = 4m/s
The momentum of the dumbbell is given by:
p = mv
p is its momentum, m is its mass, and v is its velocity.
Given values:
m = 10kg
v = 4m/s (from previous calculation)
Plug in the values and solve for p:
p = 10(4)
p = 40kg×m/s
The answer to your question would be C
Answer:
The work done against friction is 372 joules
Explanation:
It is given that,
Mass of block, m = 24 kg
Radius of the track, r = 15 m
Acceleration due to gravity, 
If the kinetic energy of the block at the bottom of the track is, 3900 J
Let P is the work done against friction. It is given by :

Here, h = r

P = 3528 J
Since it ends up with 3900 J, the work done is given by or the lost in energy will be :
W = 3900 - 3528
W = 372 joules
So, the work done against friction is 372 joules. Hence, this is the required solution.