A 20-N crate starting at rest slides down a rough 3 m long ramp, inclined at 30

Question

A 20-N crate starting at rest slides down a rough 3 m long ramp, inclined at 30 degree with the horizontal. The force of friction between crate and ramp is 6 N. What is the kinetic energy of the crate at the bottom of the ramp? Zero 2 J 8 J 12 J 32 J If both the mass and speed of a ball are tripled, the kinetic energy is increased by a factor of 1 3 6 9 27 A simple pendulum. 2.0 m in length, is released from rest when the string of the pendulum is at an angle of 25 degree from the vertical. What is the speed of the pendulum at the bottom of the swing? 0.6 m/s 0.8 m/s 1.3 m/s 1.9 m/s 4.9 m/s A 10-kg block is suspended by a string from the ceiling of an elevator. If the elevator is going down with an acceleration of 2.5 m/s^2, what is the tension of the string? 98 N 123 N 73 N I00N 95 N

Explanation / Answer

9) Kinetic energy = work done by all forces

=[mg sin 30 degree - Friction]*L

= [20*0.5 - 6]*3

= 12 J option d

10) E = 0.5mv^2

it becomes 3^2*3 = 9 times

11) v = sqrt(2gh)

= sqrt(2*9.8*2*(1- cos 25 degree))

= 1.9 m/s

12) T - mg = -ma

T = 10*(9.8-2.5)

= 73 N

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