Question

A weight lifter raises a barbell of mass 72 kg to a height of 0.65 m above his chest. The potential energy of the barbell increases in raising the barbell by approximately

Select one:

a. 459 J

b. Zero

c. –459 J

d. None of these

Three masses 2.0 kg, 3.0 kg and 6.0 kg are located at positions (3.0, 0), (6.0, 0), and (–4.0, 0), respectively, in meters from the origin (0,0). The location of the center of mass of this system is

Select one:

a. (0, 0)

b. (–1, 0)

c. (5, 0)

d. (0, –1)

A 0.1 kg steel ball is dropped straight down onto a hard horizontal floor and bounces straight up. Its speed just before and just after impact with the floor is 10 m/s. Determine the magnitude of the impulse delivered to the floor by the steel ball.

Select one:

a. 2 N.s

b. 1 N.s

c. 10 N.s

d. zero

Use the work-energy theorem to find how much net work required to accelerate a 1000 kg car from 20 m/s to 30 m/s.

Select one:

a. 2.6 X 10^4 J

b. 8.2 X 10^3J

c. 2.5 X 10^5 J

d. 1.9 X 10^5 J

A system consisting of two particles, one of which is moving to the east with a momentum of 7.0 kg.m/s while the other particle is moving to the west with a momentum of 3 kg.m/s. The total momentum (magnitude and direction) of the system is

Select one:

a. 4.0 kg.m/s, east

b. 4.0 kg.m/s, west

c. -4.0 kg.m/s, east

d. 10 kg.m/s, east

A 50 kg boy runs at a speed of 10.0 m/s and jumps onto a small cart. The cart is initially at rest. If the mass of the cart is 150 kg, what is the speed of the cart with the boy?

Select one:

a. 175 kg

b. 6.0 m/s

c. 2.5 m/s

d. 2.0 m/s

Answer #1

A barbell spins around a pivot at its center at
A.
The barbell consists of two small balls, each with mass 450
grams (0.45
kg), at the ends of a very low mass rod of length
d
= 50
cm (0.5
m; the radius of rotation is 0.25
m). The barbell spins clockwise with angular speed 120
radians/s.
We can calculate the angular momentum and kinetic energy of this
object in two different ways, by treating the object as two...

A ball of mass 0.15 kg hits the floor with a speed of 11.0 m/s
at an angle of 65° with the horizontal. The ball rebounds with a
speed of 11.0 m/s making an angle of 65° with the horizontal. Find
the magnitude of the impulse (in N.s) on the ball.
A) 1.5
B) 3.9
C) 6.0
D) 9.0
E) 3.0

A powerlifter deadlifts a 365 lb (167 kg) barbell to a height of
0.85 m, and then lowers the bar, applying a constant upward force.
The bar reaches the ground with a speed of 2 m/s. What was the work
done by the powerlifter in lowering the bar to the ground (in J)
?

A 53.0-kg boy and his 37.0-kg sister, both wearing roller
blades, face each other at rest. The girl pushes the boy hard,
sending him backward with a velocity 2.70 m/s toward the west.
Ignore friction.
(a) Describe the subsequent motion of the girl.
She will move west, in the same direction as her brother, with a
speed 2.70 m/s.She will move east, directly away from her brother
with a speed 3.87 m/s. She will move east,
directly away from her brother...

Two vehicles are approaching an intersection. One is a 2400 kg
pickup traveling at 16.0 m/s from east to west (the −x- direction),
and the other is a 1300 kg sedan going from south to north (the +y−
direction at 21.0 m/s )
a-Find the x -component of the net momentum of this
system
b-Find the y-component of the net momentum of this system.
c-What is the magnitude of the net momentum
d-What is the direction of the net momentum...

At time t = 0, a 4.0 kg particle with velocity v with arrow =
(5.0 m/s) i hat − (6.0 m/s) j is at x = 4.0 m, y = 2.0 m. It is
pulled by a 6.0 N force in the negative x direction. (a) What is
the angular momentum of the particle about the origin? (Express
your answer in vector form.) (b) What torque about the origin acts
on the particle? (Express your answer in vector form.)...

A 2.33 kg ball is
dropped from a height of 3 m. The ball then bounces back
upward a distance of 2.2 m. How much energy was lost in the
collision with the ground?
50.2 J
18.3 J
68.5 J
118.7 J
A 2.33 kg ball is
dropped from a height of 3 m. The ball then bounces back
upward a distance of 2.2 m. How much momentum does the ball have
immediately after bouncing off the ground?
5.13 kg m/s
21.6...

1) If a person holds 50 kg object at a height of 2 m above the
floor for 10 s. How much work is done? W = F×d
(2) The work done in lifting 30kg of bricks to a height of 20m
is W = m ×g × d (Formula, W = F × d but Force = m × g)
(3) A total of 4900 J is used to lift a 50-kg mass. The mass is
raised to a...

60.0-kg Beatrice on a motor scooter travels east at a speed of
15 m/s. She then reverses the direction and heads west at 10 m/s.
What is the change in her momentum?
Question 1 options:
1500 kg·m/s, west
300 kg·m/s, east
None of the above
1500 kg·m/s, east
300 kg·m/s, west
The forces acting on a plane are: lift L = 10.0
kN up, weight W = 10.0 kN down,
thrustT = 2.5 kN east, and drag D
= 2.0...

A red cart with a mass of 250 g is initially moving east at 2.25
m/s. It collides with a blue cart with a mass of 350 g that is
initially moving west at 0.750 m/s. After the collision the kinetic
energy of the two carts together is 0.200 J more than before the
collision, because the spring plunger of one of the carts pushes
them apart during the collision. After the collision, the two carts
are still moving along...

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