Question 1 of 7 Consider a ball with mass m = 5 kg. The ball is at rest on a cli

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Question 1 of 7

Consider a ball with mass m = 5 kg. The ball is at rest on a cliff 200 m above the ground.
(A) Derive an equation that describes the potential energy of the ball as a function of time after it falls off the cliff.
(B) How much kinetic energy (in Joules) does the ball have 2.1 seconds after it falls?

Question 2 of 7

A 1,180 kg cannon loaded with a 20.0 kg shell is stationary. A shell is fired from the cannon. The cannon recoils with a speed of 12.0 m/s. What is the velocity of the shell?

Question 3 of 7
A physics student throws a rock, with mass of 100 g against a brick wall at a velocity of 45 m/s. The rock splits into three pieces when it hits the wall – the first piece has a mass of 10 g, the second piece has a mass of 20 grams and the third piece has a mass of 70 g. The 10 g piece is traveling at 2 m/s and the 20 g piece is traveling at 3 m/s. What is the velocity of the 70 g piece?

Question 4 of 7

A rectangular piece of metal has dimensions 5.0 m x .50 m x 1.0 m. The metal is made of up of 85% iron ( = 7.86 g/cm3) and 15% nickel ( = 8.9 g/cm3). What is the total mass of the rectangular piece of metal?

Question 5 of 7

The force acting on a box is a constant 6.0 N for the first 10.0 m of motion. From 10.0 m to 20.0 m, the force decreases linearly from 6.0 N to 0.0 N.
(A) Find the work done on the box in the first 10.0 m.
(B) Find the work done on the box from 10.0 m to 20.0 m.
(C) Find the total work done on the box from 0.0 m to 20.0 m.

Question 6 of 7:

A 200.0 kg car moving to the right and traveling at 10.0 m/s collides with a 250.0 kg truck traveling at 15.0 m/s which is also moving to the right. The collision causes the vehicles to stick together. What is the resulting speed of the car and truck that are now stuck together?

Question 7 of 7

A force of 20.0 N is used to push a box 40.0 m across a level horizontal floor. The box weighs 10.0 N. What is the velocity of the box?

Explanation / Answer

1) A) potential energy = mgh

                                       = m *g*200 - 4.9t2

                                        = 9800 - 4.9t2

     B) kinetic energy = 0.5 * 5 * 20.58 * 20.58

                                  = 1058.841 J

2)    Here,   0 = 20 *v - 1180 *12

       => v = velocity of shell = 708 m/sec

3)   Here, 100 *45 = 10 * 2 + 20*3 + 70*v

          =>   velocity of 70 g piece =   63.14 m/sec

4)   total mass of the rectangular piece   = 7.86 * 0.85 * 2500000 + 8.9 * 0.15 * 2500000

                                                                = 20040 kg

5)   (A) the work done on the box in the first 10.0 m =   F * distance

                                                                               = 6 * 10

                                                                                = 60 J

(B)    the work done on the box from 10.0 m to 20.0 m. = area under F vs distance curve

                                                                                          = 1/2 * 10 * 6

                                                                                            = 30 J

(C)   the total work done on the box from 0.0 m to 20.0 m   = 30 + 60 J

                                                                                               = 90 J

6)    Here, 200 * 10 + 250 *15 = (200 + 250)*V

      => V =    12.77 m/sec     ------------------> resulting speed of the car and truck

7)    Here, 20 * 40 = 1/2 * 1.02 * v2

      =>     v   = 39.60 m/sec    -----------------> velocity of the box

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