Answer:
(a) Friction force = 50 N
(b) Work done by friction = 300 j
(c) Net work done = 0 j
Explanation:
We have given that the box is pulled by 6 meter so d = 6 m
Force applied on the box F = 60 N
We have have given that velocity is constant so acceleration will be zero
So to applied force will be utilized in balancing the friction force
So friction force 
Work done by friction force 
Work done by applied force 
So net work done = 300-300 = 0 j
Answer:
5. Is greater than mg, always
Explanation:
If the cone has an inclination of angle β, the sum of forces will be:
x-axis (centripetal axis):
N*sin β = m*ax where ax is the centripetal acceleration
y-axis:
N*cos β - m*g = m*ay where ay is the vertical acceleration. If the block starts falling down, ay will be negative. If the block starts sliding up, ay will be positive. If the block does not move up nor down, ay=0.
Solving for N:

If ay is positive or zero, N will be greater than mg. If ay is negative, N will be less than mg.
If the block is sliding along a horizontal circular path (not up, nor down), ay = 0, so N will always be greater than mg.
Answer:
9.4 m/s
Explanation:
According to the work-energy theorem, the work done by external forces on a system is equal to the change in kinetic energy of the system.
Therefore we can write:

where in this case:
W = -36,733 J is the work done by the parachute (negative because it is opposite to the motion)
is the initial kinetic energy of the car
is the final kinetic energy
Solving,

The final kinetic energy of the car can be written as

where
m = 661 kg is its mass
v is its final speed
Solving for v,

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