Other Physics Answers

A +40.0 𝑛𝐶 charge is placed at the origin of a coordinate system, and a −30.0 𝑛𝐶 charge is placed in the 𝑥𝑦-plane at the point(𝑥=0.200 𝑚,𝑦=−0.100 𝑚).

a) Determine the magnitude and the direction of the force that the positive charge exerts on the negative charge. Use 𝑖𝑗𝑘 notation for your result.

b) Determine the magnitude and direction of the force of the negative charge on the positive charge.

A steel rod is initially at 20°C and has a length of 2m. It has a cross-sectional area of 0.001m^2 , If it is heated to 120°C by how much does its length increase?

A block of mass 5 kg starts to slide down a frictionless plane, inclined at 25° as shown in figure 2. The block moves from rest at the top. The length of the incline is 2.0m. Find (a) the acceleration of the block, and (b) its speed when it reaches the bottom of the inclined.

A block 4kg in mass rests on a horizontal plane. What value of horizontal force is required to (a) move the block, (b) maintain the motion of the block once it is moved? The coefficients of static and kinetic friction are 0.23 and 0.18, respectively. What will the force be, if the force is instead applied 25° above the horizontal?

 A ray of light in corn oil is incident striking with an angle of incidence of 40 degrees on water. Calculate the angle of refraction to the nearest degree

The half- life period of a radioacve isotope is 30 days. If we start with 10 g of the substance, then the amount le aer 90 days is:

1. A single force F(x) = −8.0x (in newtons) acts on a 3.0-kg body. When x = 6.75 m, the speed of the body is 4.0 m/s. What is its speed at x = 2.5 m?
2. A T-shirt cannon launches a shirt at 8.00 m/s from a platform height of 5.00 m from ground level. How fast will the shirt be traveling if it is caught by someone whose hands are (a) 2.00 m from ground level? (b) 4.00 m from ground level? Neglect air drag.

1. Explain what it means for an energy source to be renewable or non-renewable.
2. A camera weighing 20 N falls from a small drone hovering 35 m overhead and enters free fall. What is the gravitational potential energy change of the camera from the drone to the ground if you take a reference point of (a) the ground being zero gravitational potential energy? (b) The drone being zero gravitational potential energy? What is the gravitational potential energy of the camera (c) before it falls from the drone and (d) after the camera lands on the ground if the reference point of zero gravitational potential energy is taken to be a second person looking out of a building 40 m from the ground?
3. A sled of mass 80 kg starts from rest and slides down a 20° incline 80 m long. It then travels for 25 m horizontally before starting back up an 9° incline. It travels 80 m along this incline before coming to rest. What is the magnitude of the net work done on the sled by friction?

1. Two people observe a leaf falling from a tree. One person is standing on a ladder and the other is on the ground. If each person were to compare the energy of the leaf observed, would each person find the following to be the same or different for the leaf, from the point where it falls off the tree to when it hits the ground: (a) the kinetic energy of the leaf; (b) the change in gravitational potential energy; (c) the final gravitational potential energy?
2. An external force acts on a particle during a trip from one point to another and back to that same point. This particle is only affected by conservative forces. Does this particle’s kinetic energy and potential energy change as a result of this trip? Explain.
3. A child jumps up and down on a bed, reaching a higher height after each bounce. Explain how the child can increase his maximum gravitational potential energy with each bounce.

1. A dropped ball bounces to one-half its original height. Discuss the energy transformations that take place. 
2. What is the physical meaning of a non-conservative force?