3. A 50-N force acts on a 2-kg orate that starts from rest. When the force has b

Question

3. A 50-N force acts on a 2-kg orate that starts from rest. When the force has been acting for 2s the rate at which it is doing work is: A) 100 W B) 1000 W c) 2500 W D) 5000 We E) 63000 W 4. Two particles interact by conservative forces. In addition, an external force acts on each particle. They complete round trips, ending at the points where they started. Which of the following must have the same values at the beginning and end of this trip? A) a total kinetic energy of the two-particle system B) the potential energy of the two-particle system C) the mechanical energy of the two-particle system D) the total linear momentum of the two-particle system E) none of the above

Explanation / Answer

(3)
F = 50 N
m = 2 kg
a = F/m = 50/2 = 25 m/s^2
t = 2 s

v = u + a*t
v = 0 + 25 * 2
v = 50 m/s

Power = Force * velocity
P = 50 * 50 W
P = 2500 W

Correct option :- (C)

(4)
As the external forces are being applied, Momentum is not conserved !!

Correct option :- None of the above

(5)
m = 6.0 * 10^-3 kg
k = 10 N/m
x = 5.0 cm = 0.05 m

Using Energy conservation,
Initial Spring potential Energy = Final Kinetic energy + Spring potential Energy
1/2 * k * x^2 = 1/2 * m * v^2 + 1/2 * k * 0.01^2
1/2 * 10 * 0.05^2 = 1/2 * 6.0 * 10^-3 * v^2 + 1/2 * 10 * 0.01^2
v = 2.0 m/s

Correct option :- (C)

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