Answer:
1.84 kJ (kilojoules)
Explanation:
A specific heat of 0.46 J/g Cº means that it takes 0.46 Joules of energy to raise the temperature of 1 gram of iron by 1 Cº.
If we want to heat 50 g of iron from 20° C to 100° C, we can make the following calculation:
Heat = (specific heat)*(mass)*(temp change)
Heat = (0.46 J/g Cº)*(50g)*(100° C - 20° C)
[Note how the units cancel to yield just Joules]
Heat = 1840 Joules, or 1.84 kJ
[Note that the number is positive: Energy is added to the system. If we used cold iron to cool 50g of 100° C water, the temperature change would be (Final - Initial) or (20° C - 100° C). The number is -1.84 kJ: the negative means heat was removed from the system (the iron).
Answer:
Option (B)
Explanation:
Light is a form of electro-magnetic waves. This light wave has distinct range of wavelength that allows it to form different colors of light. This means that the color of the light produces depending on the amount of wavelength it comprises.
The visible light ranges from Violet to Red, and this is observed as different colors when each of these electromagnetic waves strikes our eyes at a certain angle. The violet light has the shortest wavelength of about 410 nm, where the red light has the highest wavelength of about 650 nm.
Thus, the correct answer is option (B).
1.The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from mass distribution within Earth) and the centrifugal force (from the Earth's rotation).
2.How does gravity work in space? Gravity is a very important force. Every object in space exerts a gravitational pull on every other, and so gravity influences the paths taken by everything traveling through space. It is the glue that holds together entire galaxies. It keeps planets in orbit.
3.Our weight on moon is less than it would be on Earth due to a difference of the strength of gravity on the moon. The moon's gravitation force is determined by the mass and the size of the moon. Since the moon has significantly less mass than the Earth, it will not pull objects toward itself at the strength that Earth will.
Answer:
A) v₁ = 10.1 m/s t₁= 4.0 s
B) x₂= 17.2 m
C) v₂=7.1 m/s
D) x₂=7.5 m
Explanation:
A)
- Assuming no friction, total mechanical energy must keep constant, so the following is always true:
- Choosing the ground level as our zero reference level, Uf =0.
- Since the child starts from rest, K₀ = 0.
- From (1), ΔU becomes:
-
- In the same way, ΔK becomes:
-
- Replacing (2) and (3) in (1), and simplifying, we get:
- In order to find v₁, we need first to find h, the height of the slide.
- From the definition of sine of an angle, taking the slide as a right triangle, we can find the height h, knowing the distance that the child slides down the slope, x₁, as follows:
Replacing (5) in (4) and solving for v₁, we get:
- As this speed is achieved when all the energy is kinetic, i.e. at the bottom of the first slide, this is the answer we were looking for.
- Now, in order to finish A) we need to find the time that the child used to reach to that point, since she started to slide at the its top.
- We can do this in more than one way, but a very simple one is using kinematic equations.
- If we assume that the acceleration is constant (which is true due the child is only accelerated by gravity), we can use the following equation:
- Since v₀ = 0 (the child starts from rest) we can solve for a:
- Since v₀ = 0, applying the definition of acceleration, if we choose t₀=0, we can find t as follows:
B)
- Since we know the initial speed for this part, the acceleration, and the time, we can use the kinematic equation for displacement, as follows:
- Replacing the values of v₁ = 10.1 m/s, t₂= 2.0s and a₂=-1.5m/s2 in (10):
C)
- From (6) and (8), applying the definition for acceleration, we can find the speed of the child whem she started up the second slope, as follows:
D)
- Assuming no friction, all the kinetic energy when she started to go up the second slope, becomes gravitational potential energy when she reaches to the maximum height (her speed becomes zero at that point), so we can write the following equation:
- Replacing from (12) in (13), we can solve for h₂:
- Since we know that the slide makes an angle of 20º with the horizontal, we can find the distance traveled up the slope applying the definition of sine of an angle, as follows:
Answer:
Force = -91.7 Newton
Explanation:
Given the following data;
Mass = 47 kg
Time = 4.1 seconds
Initial velocity = 8 m/s
Since the object comes to a stop, its final velocity would be equal to zero.
To find the force required to bring it to stop;
First of all, we would determine the acceleration of the object;
Mathematically, acceleration is given by the equation;
Substituting into the equation;
Acceleration, a = -1.95 m/s²
Next, we would determine the force required to bring the object to stop;
Force = -91.65 ≈ 91.7 Newton