You view your face in a concave mirror of focal length 20 cm and wish it to be magnified by a factor of 1.5. What should you do?
Answers
Answer:
u = 6.667 cm
Explanation:
given,
Focal length of the concave mirror, f = 20 cm
magnification factor = 1.5
we know,
v is the distance of the image
u is the distance of the object
v = -1.5 u
Using mirror formula
u = 6.667 cm
distance of the person from the mirror is equal to 6.667 cm.
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False
Answers
Answers
Answer:
Explanation:
Horizontal Launch
When an object is thrown horizontally with a speed v from a height h, it describes a curved path ruled by gravity until it eventually hits the ground.
The horizontal component of the velocity is always constant because no acceleration acts in that direction, thus:
vx=v
The vertical component of the velocity changes in time because gravity makes the object fall at increasing speed given by:
The horizontal component of the velocity is always the same:
The vertical component at t=5.5 s is:
B. Improved strength across the entire range of motion
C. Improved joint flexibility
D. Motivational
Answers
Answer: C. Improved joint flexibility
Explanation:
Isometric exercises are the exercises which involves the contraction of particular muscles or group of muscles. In these exercises the muscles do not change their length and the joints does not move. These are the exercises which are done in one position. These exercises are performed in order to obtain strength during training exercises during which the muscle length and joint angles do not basically change. These exercises are high intensity exercises and contributes to the building of muscles and burning of fat.
On the basis of the above information, A. Rapid strength improvement is the correct option.
Final answer:
The primary advantage of isometric exercise is rapid strength improvement in a specific area, not necessarily improved flexibility or range of motion.
Explanation:
The best answer that describes an advantage of isometric exercise is A. Rapid strength improvement. Isometric exercises are often used for rehabilitation and building strength, as they involve the contraction of a specific set of muscles in a static position. This type of exercise does not involve the muscle changing length or the joint angle changing, which allows for an increase in strength in a very focused manner.
This does not necessarily mean that isometric exercises enhance joint flexibility (C) or improve strength across the entire range of motion (B) as the movement is static. The motivation aspect (D) can differ from person to person, but it's not a direct physical benefit of isometric exercises.
Learn more about isometric exercise
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Answers
Explanation:
Atomic number is defined as the total number of protons present in an element.
Each element of the periodic table has different atomic number because each of them have different number of protons.
For example, atomic number of Na is 11, and atomic number of Ca is 20.
On the other hand, atomic mass is the sum of total number of protons and neutrons present in an atom.
For example, atomic mass of nitrogen is 14 that is, it contains 7 protons and 7 neutrons.
Thus, we can conclude that all atoms of the same element must have the same number of protons.
Answer: Protons
Explanation: The number of protons corresponds to the atomic number.
2. How fast would a 0.25 kg football have to be traveling to have the same momentum as a 0.05 kg bullet travelling 500 m/s?
3. Sarah, who has a mass of 55 kg, is riding in a car at 20 m/s. She sees a cat crossing the street and slams on the brakes! Her seat-belt stops her from flying forward, bringing her to rest in 0.5 seconds. How much force did the seat-belt put on Sarah?
Answers
p = mv
p =75(18) = 1350 kg-m/s
2. We equate the momentum of the two objects
0.25 v = 0.05 (500)
v = 100 m/s
3. We use the formula for impulse:
Δmv = FΔt
55(20) = F(0.5)
F = 2200 N
1)
P = mv
P=75 (18) = 1350 kg-m/s
2)
0.25 v= 0.05 (500)
V= 100 m/s
3)
∆ mv = F∆t
55(20) =F(0.5)
2.7m/s
7.2m/s
Answers
-- Gravitational potential energy = (mass) x (gravity) x (height)
-- Kinetic energy (of a moving object) = (1/2) (mass) x (speed)²
When the pendulum is at the top of its swing,
its potential energy is
(mass) x (gravity) x (height)
= (5 kg) x (9.8 m/s²) x (0.36 m)
= (5 x 9.8 x 0.36) joules
= 17.64 joules .
Energy is conserved ... it doesn't appear or disappear ...
so that number is exactly the kinetic energy the pendulum
has at the bottom of the swing, only now, it's kinetic energy:
17.64 joules = (1/2) x (mass) x (speed)²
17.64 joules = (1/2) x (5 kg) x (speed)²
Divide each side by 2.5 kg:
17.64 joules / 2.5 kg = speed²
Write out the units of joules:
17.64 kg-m²/s² / 2.5 kg = speed²
(17.64 / 2.5) (m²/s²) = speed²
7.056 m²/s² = speed²
Take the square root
of each side: Speed = √(7.056 m²/s²)
= 2.656 m/s .
Looking through the choices, we're overjoyed to see
that one if them is ' 2.7 m/s '. Surely that's IT !
_______________________________
Note:
The question asked for the pendulum's 'velocity', but our (my) calculation
only yielded the speed.
In order to describe a velocity, the direction of the motion must be known,
and the question doesn't give any information on exactly how the pendulum
is hanging, and how it's swinging.
We know that at the bottom of its swing, the motion is completely horizontal,
but we have no clue as to what direction. So all we can discuss is its speed.