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A proton with an initial speed of 800,000 m/s is brought to rest by an electric field. a. Did the proton move into a region of higher potential or lower potential? b. What was the potential difference that stopped the proton? c. What was the initial kinetic energy of the proton, in electron volts?

A 2.0 kg book is lying on a 0.75-m-high table. You pick it up and place it on a bookshelf 2.3 m above the floor. During this process, 
How much work does gravity do on the book?

To throw a discus, the thrower holds it with a fully outstretched arm. Starting from rest, he begins to turn with a constant angular acceleration, releasing the discuss after making one complete revolution. The diameter of the circle in which the discus moves is about 1.8 m. If the thrower takes 1.0 s to complete one revolution, starting from rest, what will be the speed of the discus at release?

A550-N physics student stands on a bathroom scale in an elevator that is supported by a cable. The combined mass of student plus elevator is 850 kg. As the elevator starts moving, the scale reads 450 N. 
(a) Find the acceleration of the elevator (magnitude and direction). 
(b) What is the acceleration if the scale reads 670 N? 
(c) If the scale reads zero, should the student worry? Explain. 
(d) What is the tension in the cable in parts (a) and (с)? 

A hot-air balloonist, rising vertically with a constant velocity of magnitude 5.00 m/s, releases a sandbag at an instant when the balloon is 40.0 m above the ground. After the sandbag is released, it is in free fall. (a) Compute the position and velocity of the sandbag at 0.250 s and 1.00 s after its release. (b) How many seconds after its release does the bag strike the ground? (c) With what magnitude of velocity does it strike the ground? (d) What is the greatest height above the ground that the sandbag reaches? (e) Sketch $a_y-t,v_{y}t$, and y-t graphs for the motion.

Two parallel plates have equal and opposite charges. When the space between the plates is evacuated, the electric field is $E=3.20\times {10}^5\mathrm{V}/\mathrm{m}$. When the space is filled with dielectric, the electric field is $E=2.50\times {10}^5\mathrm{V}/\mathrm{m}$. (a) What is the charge density on each surface of the dielectric? (b) What is the dielectric constant?

The rope and pulley have negligible mass, and the pulley is frictionless. The coefficient of kinetic friction between the 
8.00-kg block and the tabletop is ${\displaystyle \mu k=0.250}$. The blocks are released from rest. Use energy methods to calculate the speed of the 6.00-kg block after it has descended 1.50 m. 

A bicycle with 0.80-m-diameter tires is coasting on a level road at 5.6 m/s. A small blue dot has been painted on the tread of the rear tire. a. What is the angular speed of the tires? b. What is the speed of the blue dot when it is 0.80 m above the road? c. What is the speed of the blue dot when it is 0.40 m above the road?

An antelope moving with constant acceleration covers the distance between two points 70.0 m apart in 6.00 s. Its speed as it passes the second point is 15.0 m/s. What are (a) its speed at the first point and (b) its acceleration?

A fan blade rotates with angular velocity given by ${\displaystyle {\omega }_z\left(t\right)=\gamma -\beta t^2}$, where ${\displaystyle \gamma =5.00ra\frac{d}{s}}$ and ${\displaystyle \beta =0.800ra\frac{d}{s^3}}$. (a) Calculate the angular acceleration as a function of time. (b) Calculate the instantaneous angular acceleration ${\displaystyle a_z}$ at ${\displaystyle t=3.00s}$ at t = 3.00 s and the average angular acceleration ${\displaystyle a_{av-z}}$ for the time interval t = 0 to t = 3.00 s. How do these two quantities compare? If they are different, why?

The mass of Venus is 81.5% that of the earth, and its radius is 94.9% that of the earth. 
(a) Compute the acceleration due to gravity on the surface of Venus from these data. 
(b) If a rock weighs 75.0 N on earth, what would it weigh at the surface of Venuse?

In getting ready to slam-dunk the ball, a basketball player starts from rest and sprints to a speed of 6.0 m/s in 1.5 s. Assuming that the player accelerates uniformly, determine the distance he runs.

A jet plane lands with a speed of 100 m/s and can accelerate at a maximum rate of ${\displaystyle -5.00\frac{m}{s^2}}$ as it comes to rest. Can this plane land on a small tropical island airport where the runway is 0.800 km long?

It takes the elevator in a skyscraper 4.0 s to reach its cruising speed of 10 m/s. A 60 kg passenger gets aboard on the ground floor. What is the passengers

The air pressure in the tires of a ${\displaystyle 980-kg}$ car is ${\displaystyle 3.0\times {10}^5\frac{N}{m^2}}$. Determine the average area of contact of each tire with the road.

A horizontal rope is tied to a 50 kg box on frictionless ice. What is the tension in the rope if a. The box is at rest? b. The box moves at a steady 5.0 m/s? c. The box has ${\displaystyle v_x=5.0\frac{m}{s}}$ and ${\displaystyle a_x=5.0\frac{m}{s^2}?}$

A rocket starts from rest and moves upward from the surface of the earth. For the first 10.0 s of its motion, the vertical acceleration of the rocket is given by ${\displaystyle a_y=12.80\frac{m}{s^3}}$ )t, where the + y-direction is upward. (a) What is the height of the rocket above the surface of the earth at t = 10.0 s? (b) What is the speed of the rocket when it is 325 m above the surface of the earth?

A bicycle wheel has an initial angular velocity of 1.50 rad/s. (a) If its angular acceleration is constant and equal to ${\displaystyle 0.200ra\frac{d}{s^2}}$, what is its angular velocit at t=2.50 s? (b) Through what angle has the wheel turned between t = 0 and t = 2.50 s?

At a certain location, wind is blowing steadily at 10 m/s. Determine the mechanical energy of air per unit mass and the power generation potential of a wind turbine with 60-m-diameter blades at that location. Take the air density to be ${\displaystyle 1.25 \frac{kg}{m^3}}$.