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larisa [96]
3 years ago
5

A 144-g baseball moving 26 m/s strikes a stationary 5.25-kg brick resting on small rollers so it moves without significant frict

ion. After hitting the brick, the baseball bounces straight back, and the brick moves forward at 1.05 m/s
(a) What is the baseball spped after the collision?
(b) Find the total kinetic energy before and after the collision.
Physics
1 answer:
Monica [59]3 years ago
6 0

Answer:

a. v_{f1}=-12.28m/s

b. K_{Einitial} = 48.672J,  K_{E(final)} = 13.75 J

Explanation:

Let the velocity of the ball after collision is v m/s, By the law of momentum conservation:

p_i=p_f

m_1*u_1+m_2*u_2 = m_1*v_1 + m_2*v_2

0.144kg*26m/s + 5.25kg*0 = 0.144kg*v_{f1} + 5.25kg*1.05m/s

Solve to vf1

v_{f1}=\frac{0.144kg*26m/s-5.25kg*1.05m/s}{0.144kg}

v_{f1}=-12.28m/s

(b)

K_E(initial) = 1/2*m_1u_1^2

K_E = 1/2*0.144kg*(26m/s)^2

K_{Einitial} = 48.672J

K_{E(final)} = 1/2*m_1v_1^2 + 1/2*m_2v_2^2

K_{E(final)} = 1/2*0.144kg*(12.28m/s)^2 + 1/2*5.25 x (1.05m/s)^2

K_{E(final)} = 13.75 J

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Martha must carry a 45 N package up three flights of stairs. Each flight of stairs has a height of 2.3m, and the actual distance
Darina [25.2K]

Answer:

310.5 J

Explanation:

The total work done by Martha is equal to the increase in gravitational potential energy of the package, which is equal to

\Delta U = mg\Delta h

where

(mg) = 45 N is the weight of the package

\Delta h is the increase in height of the package

The package is carried up 3 flights of stairs, each one with a height of 2.3 m, so the total increase in heigth is

\Delta h = 3 \cdot 2.3 m=6.9 m

And so, the work done by Martha is

U=(45 N)(6.9 m)=310.5 J

3 0
3 years ago
A girl pulls on a 10-kg wagon with a constant horizontal force of 30 n. if there are no other horizontal forces, what is the wag
olga2289 [7]
Force = mass * acceleration
F = ma

Given m = 10 kg, F = 30 N;

F = ma
30 = 10a

Solving for a:
a = 3 m/s^2

The acceleration is 3 meters per second squared.
8 0
3 years ago
A person just supports a mass of 20kg suspended from a rope.
Georgia [21]

Answer:

F = 200 N

Explanation:

Given that,

The mass suspended from the rope, m = 20 kg

We need to find the resultant force acting on the rope. The resultant force on the rope is equal to its weight such that,

F = mg

Where

g is acceleration due to gravity

Put all the values,

F = 20 kg × 10 m/s²

F = 200 N

So, the resultant force on the mass is 200 N.

7 0
2 years ago
If the resistance of a circuit increases, that means that the current has to
Gnoma [55]

Answer:

If resistance increases current decreases.

Explanation:

  • Current is <em>inversely proportional</em> to the resistance.
  • from the relation given below, we can clearly see the relation between current and resistance;

                              V=IR

                              I ∝ 1/R

This relation shows that when resistance increases,current decreases.

4 0
3 years ago
A 4 kg textbook sits on a desk. It is pushed horizontally with a 50 N applied force against a 15 N frictional force.
GarryVolchara [31]

a) See free-body diagram in attachment

b) The book is stationary in the vertical direction

c) The net horizontal force is 35 N in the forward direction

d) The net force on the book is 35 N in the forward horizontal direction

e) The acceleration is 8.75 m/s^2 in the forward direction

Explanation:

a)

The free-body diagram of a body represents all the forces acting on the body using arrows, where the length of each arrow is proportional to the magnitude of the force and points in the same direction.

From the diagram of this book, we see there are 4 forces acting on the book:

- The applied force, F = 50 N, pushing forward in the horizontal direction

- The frictional force, F_f = 15 N, pulling backward in the horizontal direction (the frictional force always acts in the direction opposite to the motion)

- The weight of the book, W=mg, where m is the mass of the book and g=9.8 m/s^2 is the acceleration of gravity, acting downward. We can calculate its magnitude using the mass of the book, m = 4 kg:

W=(4)(9.8)=39.2 N

- The normal reaction exerted by the desk on the book, N, acting upward, and balancing the weight of the book

b)

The book is in equilibrium in the vertical direction, therefore there is no motion.

In fact, the magnitude of the normal reaction (N) exerted by the desk on the book is exactly equal to the weight of the book (W), so the equation of motion along the vertical direction is

N-W=ma

where a is the acceleration; however, since N = W, this becomes

a=0

And since the book is initially at rest on the desk, this means that there is no motion.

c)

We said there are two forces acting in the horizontal direction:

- The applied force, F = 50 N, forward

- The frictional force, F_f = 15 N, backward

Since they act along the same line, we can calculate their resultant as

\sum F = F - F_f = 50 - 15 = 35 N

and therefore the net force is 35 N in the forward direction.

d)

The net force is obtained as the resultant  of the net forces in the horizontal and vertical direction. However, we have:

- The net force in the horizontal direction is 35 N

- The net force in the vertical direction is zero, because the weight is balanced by the normal reaction

Therefore, this means that the total net force acting on the book is just the net force acting on the horizontal direction, so 35 N forward.

e)

The acceleration of the book can be calculated by using Newton's second law:

\sum F = ma

where

\sum F is the net force

m is the mass

a is the acceleration

Here we have:

\sum F = 35 N (in the forward direction)

m = 4 kg

Therefore, the acceleration is

a=\frac{\sum F}{m}=\frac{35}{4}=8.75 m/s^2 (forward)

Learn more about forces, weight and Newton's second law:

brainly.com/question/8459017

brainly.com/question/11292757

brainly.com/question/12978926

brainly.com/question/11411375

brainly.com/question/1971321

brainly.com/question/2286502

brainly.com/question/2562700

#LearnwithBrainly

8 0
3 years ago
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