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A car of mass 1000 kg is travelling at 15 m/s. The driver applies the brakes for 4 seconds, slowing the car to 5 m/s. What is the average power output of the brakes over the 4 seconds? Assume there are no other forces acting on the car.

Kinetic Energy, EK=(1/2)mv². Energy is conserved, so the work done by the brakes, W, must be equal to the change in kinetic energy of the car, ∆EK. Therefore: W = ∆EK = (1/2)1000(15

Answered by Adam H. • Physics tutor

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An electron moving at 1000 m/s annihilates with a stationary positron. What is the frequency of the single photon produced?

The first thing to be aware of is that the frequency of a photon will depend on two things, its wavelength (c=fλ ) and its energy (E=hf). There is no information regarding the wavelength of the photon, bu...

Answered by Lawrence M. • Physics tutor

1499 Views

A cannon is fired at 30 degrees from the ground and the cannonball has initial velocity of 15 m/s. What is the height of the highest point the cannonball reaches and how far is this point horizontally from the cannon?

With this type of question always draw a diagram with the values on it. We can assume the positive direction is upwards. Start with considering the vertical motion and use SUVAT. s= ? (this is what we are...

Answered by Elena V. • Physics tutor

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2 identical trolleys of mass M(one is loaded with 2 blocks of mass m) are on a ramp inclined at 35° and are connected by a wire that passes around a pulley at the top of the ramp. They are released and accelerate accordingly. Show that a=(mgsin35°)/(M+m).

Construction of Free Body Diagrams of the Trolleys and resolving the forces (Weight and Tension) components acting parallel to the ramp (assuming friction and air resistance are negligible) show that for ...

Answered by Neophytos V. • Physics tutor

3009 Views

If a box full of feathers and a box full of bricks were to be dropped at the same time and from the same height, which one would hit the ground first?

They would hit to ground at the same time. This is because they would both accelerate to the ground at 10m/s^2 due to gravity regardless of what their mass is. This is contrary to one might intuit when co...

Answered by Adam Yanis C. • Physics tutor

10547 Views