The first rule of vectors is that the horizontal and vertical components are separate. Disregarding air resistance, the only thing we have to worry about is gravity.
The appropriate suvat to use for the vertical component is v = u +at
I will take a to be -9.81, you may have to change it to be 10 if your qualification likes g to be 10.
v = 30 + (-9.81x2)
v = 30 - 19.62
=10.38m/s
Therefore we know that after 2.0 s the vertical component will be 10.38ms^-1, ie 10m/s as the answers given are all to 2sf.
The horizontal component is completely separate to the vertical component and since there is no air resistance, it will remain constant throughout the projectiles trajectory. Therefore it will remain at 40ms^-1.
Combining this together we get:
(1) vx=40m/s and vy=10m/s
The final velocity of the two pucks is -5 m/s
Explanation:
We can solve the problem by using the law of conservation of momentum.
In fact, in absence of external force, the total momentum of the two pucks before and after the collision must be conserved - so we can write:

where
is the mass of each puck
is the initial velocity of the 1st puck
is the initial velocity of the 2nd puck
v is the final velocity of the two pucks sticking together
Re-arranging the equation and solving for v, we find:

Learn more about momentum:
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The weight changes but the mass will stay the same.
Answer:
a) Em= K +U, b) Em= K
Explanation:
The system in this case is formed by the mobilizes and the hill.
Let's write the expressions correctly and completely.
a) When the car moves in the path, the mechanical energy is the siua of the kinetic energy of the car and the potential energy of the car when going up the hill.
Em = K + U
be) when the car moves in the flat part all the mechanical energy is formed by its kinetic energy that is calculated with the mass and speed of the car
Em = K
c) When the car goes up the hill the energy the mechanical energy is conserved, but part of the kinetic energy is transformed into potential energy.
Answer:
The light wave has a longer wavelength and has the greater speed.
Explanation:
light has a far more greater speed than sound. The speed of sound in air is about 343m/s while that of light is around 
wavelength (λ) =
since the frequencies of sound and light are same from the question, the wavelength would depend on the magnitude of their velocities. Light with a higher speed would have a longer wavelength.