A 4.0 kg stone slides from rest down a hill 5.0 m high and is observed to be mov

Question

A 4.0 kg stone slides from rest down a hill 5.0 m high and is observed to be moving at 8.0 m/s at the bottom. During this process 68 J of thermal energy have been produced A) True B) False A box slides down a smooth ramp, starting from rest at a height 5.4 m. When it reaches the it's moving at speed v. It then continues to slide up a second smooth ramp. At what height is its speed equal to v/3? A) 5.4 m B) 2.7 m C) 3.6 m D) 3.2 m E) 4.8 m A 1200 kg cannon fires a 100.0 kg cannonball at 3.5 m/s. What is the recoil velocity of the cannon? Assume that frictional forces are negligible and the cannon is fired horizontally. A) 3.5 m/s B) 3.5 m/s C) 3.2 m/s D) 2.9 m/s Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a smaller magnitude? A) The two forces are equal. B) the second force (at the doorknob) C) the first force (at the midpoint) A horizontal disk rotates about a vertical axis through its center, Point Q is midway between the center and the rim of the disk, and point P is on the rim. If the disk turns with constant angular velocity, which of the following statements about it is true? A) The linear acceleration of P is twice as great as the linear acceleration of Q. B) The linear acceleration of Q is twice as great as the linear acceleration of P. C) The angular velocity of Q is twice as great as the angular velocity of P. D) P and Q have the same linear acceleration. (Draw free-body diagrams for block A and Block B. Show all your work clearly 4 points) Two blocks are connected by a string that goes over an ideal pulley as shown in the figure. Block A has a mass of 3.00kg and can slide over a rough plane inclined 30.0 degree to the horizontal. The coefficient of kinetic friction between block A and the plane is 0.400. Block B has a mass of 2.77 kg. What is the acceleration of the blocks? A) 5.35 m/s^2 B) 3.12 m/s^2 C) 1.96 m/s^2 D) 0.392 m/s^2 E) 0.00 m/s^2

Explanation / Answer

6) Initial energy = P.E. + K.E = m*g*h + (1/2)mv2 = 4*9.8*5 + 0 = 196 J

    final energy = P.E. + K.E = m*g*h + (1/2)mv2 = 0 + 0.5*4*82 = 128 J

Energyn lost in the form of thermal energy = initial energy - final energy = 196 -128 = 68 J

7) Let the mass of the box be m. Applying conservation of energy.

Total energy, E= mgh = (1/2)mv2    ....................1)

or    (2gh)= v2

or v2 = (2*g*5.4)    m2/s2                ......(as h=5.4 m )

Now total energy at height h',

E = mgh' + (1/2)m(v/3)2 = mgh    .........................from 1)

or        gh' + v2/18 = g*5.4

or       gh' + 2g*5.4/18 = g*5.4

or       h' = 5.4 - 5.4/9 = 4.8 m

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.