There are two conditions necessary for total internal reflection, which is when light hits the boundary between two mediums and reflects back into its original medium:
Light is about to pass from a more optically dense medium (slower) to a less optically dense medium (faster).
The angle of incidence is greater than the defined critical angle for the two mediums, which is given by:
θ = sin⁻¹(
/
)
Where θ = critical angle, = refractive index of faster medium, = refractive index of slower medium.
Choice C gives one of the above necessary conditions.
Answer:
a) 0.25m
b) 5 m/s
Explanation:
When the spring is compressed both boxes are moving with the same velocity, so applying the principle of linear momentum conservation:
Now applying the principle of energy conservation:
We got that the maximum compression is 0.25m.
(I assume that the 4 directions north-south-east-west are meant with respect to the wire seen from the top.)
We can use the right-hand rule to understand the direction of the magnetic field generated by the wire. The thumb follows the direction of the current in the wire (upward), while the other fingers give the direction of the field in every point around the wire. Seen from the top, the field has an anti-clockwise direction. Therefore, if we take a point at east with respect to the wire, in this point the field has direction south.
Answer:
a) 8.61 m/s, b) 5.73 m
Explanation:
a) During the collision, momentum is conserved.
mv = (m + M) V
(12.5 g) (86.4 m/s) = (12.5 g + 113 g) V
V = 8.61 m/s
b) After the collision, energy is conserved.
Kinetic energy = Work done by friction
1/2 (m + M) V² = F d
1/2 (m + M) V² = N μk d
1/2 (m + M) V² = (m + M) g μk d
1/2 V² = g μk d
d = V² / (2g μk)
d = (8.61 m/s)² / (2 × 9.8 m/s² × 0.659)
d = 5.73 m
Notice we used the kinetic coefficient of friction. That's the friction when an object is moving. The static coefficient of friction is the friction on a stationary object. Since the bullet/block combination is sliding across the surface, we use the kinetic coefficient.
Explanation:
The mass of a ball, m = 2 kg
It is traveling with a speed of 10 m/s
The ball's kinetic energy just as it leaves the boy's hand is calculated as follows :
The ball's kinetic energy just as it leaves the boy's hand is 100 J. The potential energy of the ball when it reaches the highest point is same as the kinetic energy as it leaves the boy's hand.
Hence, the required kinetic and potential energy is 100 J.
