Flashcards in Chapter 7 Deck (9):

1

## A 15000 kg railroad car travels alone on a level frictionless track with a constant speed of 25.0 m/s. A 6000 kg load, initially at rest, is dropped onto the car. What will be the car's new speed?

### 17.86 m/s

2

## Calculate the force exerted on a rocket, given that the propelling gases are expelled at a rate of 1360 kg/s with a speed of 3.9 104 m/s (at the moment of takeoff).

### 53040000 N

3

## A 0.145 kg baseball pitched at 36.0 m/s is hit on a horizontal line drive straight back toward the pitcher at 52.0 m/s. If the contact time between bat and ball is 3.00 ✕ 10-3 s, calculate the average force between the ball and bat during contact.

### 4253.3 N

4

##
A tennis ball of mass m = 0.065 kg and speed v = 60 m/s strikes a wall at a 45° angle and rebounds with the same speed at 45°. What is the impulse given to the wall?

http://www.webassign.net/giancoli5/7_29.gif

Magnitude

Direction

a. in the direction of the ball's original motion

b.opposite the direction of the ball's original motion

c.normal and away from the wall

d.normal and into the wall

e.in the direction of the ball's final motion

f.opposite the direction of the ball's final motion

###
5.51 Ns

d.normal and into the wall

5

##
A ball of mass 0.340 kg moving east (+x direction) with a speed of 4.00 m/s collides head-on with a 0.500 kg ball at rest. If the collision is perfectly elastic, what will be the speed and direction of each ball after the collision?

ball originally at rest

ball originally moving east

###
ball originally at rest:

3.238 m/s E

ball originally moving east:

.7620 m/s W

6

##
Two billiard balls of equal mass undergo a perfectly elastic head-on collision. If the speed of ball 1 was initially 6.00 m/s, and that of ball 2 was 7.00 m/s in the opposite direction, what will be their speeds after the collision?

ball 1

ball 2

###
ball 1: -7 m/s

ball 2: 6 m/s

7

## A ball of mass m makes a head-on elastic collision with a second ball (at rest) and rebounds with a speed equal to one-fifth its original speed. What is the mass of the second ball? (Use the following as necessary: m)

### m2= 1.5m

8

##
An explosion breaks an object into two pieces, one of which has 1.5 times the mass of the other. If 7600 J were released in the explosion, how much kinetic energy did each piece acquire?

heavier piece

lighter piece

###
heavier piece: 3040 J

lighter piece: 4560 J

9