An 90 Kg crate is pulled 6m by a horizontal force of 700 N. The force pulls agai

Question

An 90 Kg crate is pulled 6m by a horizontal force of 700 N. The force pulls against a friction force with coefficient mu = 0.2 The work done by the net force is A stationary rocked is fired with an acceleration of 13 m/s^2. After 20s its fuel runs out. Calculate the total time it takes for the rocket to fall back to the ground. A 10-g bullet moving at 1100 m/s strikes and passes through a 4.0 kg block initially at rest as shown. The bullet emerges with a speed of 280 m/s. How high does the block rise? A motorist drives 60 mph for 2 hours due east, then 65 mph for 3 hours due north. Calculate the motorist's average velocity for the entire trip. A rocket is fired vertically from rest with a constant acceleration of 6 m/s^2. 10 s later the fuel is all burned up and the rocket becomes a free falling object eventually falling back to the ground. How high did the rocket reach before falling down?

Explanation / Answer

8) mass, m = 90 kg
distance pulled, d = 6 m
force, F = 700 N
friction coefficient, mu = 0.2
Net force = F -mu*mg = 700 - 0.2*90*9.81 = 523.42 N
Workdone = 523.42*6 = 3140.52 J ( option b)

9) net height, h = 0.5*13*20^2 + (13*20)^2/2*9.81 = 6045.463 m [ using the three kinematic equations of motion]
time to fall = sqroot(6045.463*2/9.81)+ 20 s + 13*20/9.81 = 35.107 s + 20s + 26.503 = 81.610 s = option c

10)from conservation of momentum
0.01*1100 = 4*v + 0.01*280
v = 2.05 m/s
s = v^2/2g = 0.214 m = option B

11) distance = sqroot(120^2 + 195^2) = 228.965 mi
time = 5 hrs
average speed = 45.793 mi/hr

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