An object moving in a circle at a constant speed has no acceleration.

True or false.

Marc is in no way athletic, never goes to the gym, and gets winded by just walking up some stairs. When he was in his undergrad, Marc used to be late for the bus frequently. One time, he was running at 5 m/s to catch a bus that he was late for while the bus was 40 m away. Marc then noticed the bus started to drive away with a constant acceleration of a = 0.17 m/s^2 (Marc can notice these things).

1. (a) How long does Marc have to continuing running at 5 m/s to catch the bus? How much distance has he covered in that time?

2. (b) When Marc reaches the bus, how fast is the bus traveling?

3. (c) You may have noticed that the mathematical process in part (a) produces two solutions. Explain the physical meaning of the second solution. How fast is the bus traveling at this point?

4. (d) Now, it’s a miracle Marc was able to even achieve a speed of 5 m/s. In all honesty, he can likely only reach 3.5 m/s (at best). At this speed, would Marc catch the bus?

5. (e) What is the minimum speed someone would need to be able to run to catch the bus under these conditions? What would be their running time be and total distance traveled?

what is the maximum efficiency of a solar cell? recall the temperature of the sun is 5600 K.

A helium balloon ride lifts up passengers in a basket. Assume the density of air is 1.28 kg/m³ and the density of helium in the balloon is 0.18 kg/m³. The radius of the balloon (when filled) is R = 5.4 m. The total mass of the empty balloon and basket is m_b = 122 kg and the total volume is V_b = 0.064 m³. Assume the average person that gets into the balloon has a mass m_p = 73 kg and volume V_p = 0.079 m³.

1) What is the volume of helium in the balloon when fully inflated?

m³

2) What is the magnitude of the force of gravity on the entire system (but with no people)? Include the mass of the balloon, basket, and helium.

N

3) What is the magnitude of the buoyant force on the entire system (but with no people)? Include the volume of the balloon, basket, and helium.

N

4) What is the magnitude of the force of gravity on each person?

N

5) What is the magnitude of the buoyant force on each person?

N

6) How many FULL people can the balloon lift up? (Your answer must be an integer.)

people

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3. A car with mass 1200 kg travels at 35 m/s, while a second car with mass 1500 kg travels at 25 m/s. The two cars collide in a perfectly inelastic collision.

a) What is the final velocity (speed and direction) if the first car was travelling north and the second travelling south?   
b) If the first car were travelling north and the second were travelling east?

4. Sam stands on a 4-m-long hanging scaffold suspended by two ropes, one at either end.

a) If Sam has a mass of 80 kg, and the scaffold has a mass of 40 kg, what is the minimum tension that could be felt by a single rope if the system is in static equilibrium?
b) What is the maximum tension that could be felt by a single rope if the system is in static equilibrium?

Calculus-based physics rotational inertia:

a) Two disks are mounted (like a merry-go-round) on low-friction bearings on the same axle and can be brought together so that they couple and rotate as one unit. The first disk, with rotational inertia 2.56 kg·m² about its central axis, is set spinning counterclockwise (which may be taken as the positive direction) at 309 rev/min. The second disk, with rotational inertia 7.07 kg·m² about its central axis, is set spinning counterclockwise at 760 rev/min. They then couple together. (a) What is their angular speed after coupling? If instead the second disk is set spinning clockwise at 760 rev/min, what are their (b) angular velocity (using the correct sign for direction) and (c) direction of rotation after they couple together?

b) The uniform rod (length 0.309 m) in the figure rotates in the plane of the figure about an axis through one end, with a rotational inertia of 0.275 kg·m². As the rod swings through its lowest position, it collides with a 0.242 kg putty wad that sticks to the end of the rod. If the rod's angular speed just before the collision is 3.21 rad/s, what is the angular speed of the rod-putty system immediately after the collision?

1. Suppose rain falls vertically into an open cart rolling along a straight horizontal track with negligible friction. As a result of the accumlating water, the kinetic energy of the cart.

a. increases
b. does not change
c. decrease

2. two marbles, one twice as heavy as the other, are dropped to the ground from the roof of a building. Just before hitting the ground, the heavier marble has

a. as much kinetic energy as the lighter one
b. twice as much kinetic energy as the lighter one
c. half as much kinetic energy as the lighter one
d. four times as much kinetic energy as the lighter one
e. impossible to determine

3. A person attempts to knock down a large wooden bowling pin by throwing a ball at it. The person has two balls of equal size and mass, one made of rubber and the other of putty. The rubber ball bounces back, while the ball of putty sticks to the pin. Which ball is most likely to topple the bowling pin?

a. the rubber ball
b. the ball of putty
c. makes no difference

4. We launch a 1 kg block with spring along a rough surface (coefficient of kinetic friction of 0.45).
a.If a spring compression of 0.25m launches the block a total of 2.5m, what is the spring constant of the spring?
b.How much compression is required to reach a target 5.0m away?

1. Evaluate the heat exchange through the fin and compare it to the case where the tip is insulated. Discuss the length of fin when the two treatments are approximately the same. (hint: you might find expressing the solution to the differential equation in the e^xform to be more convenient)

A piston in a gasoline engine is in simple harmonic motion. The engine is running at the rate of 3 410 rev/min. Taking the extremes of its position relative to its center point as ±4.50 cm.

(a) Find the magnitude of the maximum velocity of the piston.
m/s

(b) Find the magnitude of the maximum acceleration of the piston
km/s²

Is there any general relation between the amount of charge possesses and its range in air? Were any bremsstrahlung produced in an experiment of absorption of beta particles ? How may bremsstrahlung production be minimized?

A 67 kg window cleaner uses a 11 kg ladder that is 5.9 m long. He places one end on the ground 2.7 m from a wall, rests the upper end against a cracked window, and climbs the ladder. He is 3.3 m up along the ladder when the window breaks. Neglect friction between the ladder and window and assume that the base of the ladder does not slip. When the window is on the verge of breaking, what are (a) the magnitude of the force on the window from the ladder, (b) the magnitude of the force on the ladder from the ground, and (c) the angle (relative to the horizontal) of that force on the ladder?

In a ballistic pendulum experiment, projectile 1 results in a maximum height h of the pendulum equal to 2.2 cm . A second projectile causes the pendulum to swing twice as high, h2 = 4.4 cm . The second projectile was how many times faster than the first?

What is the density of a woman who floats in fresh water with 2.25% of her volume above the surface? (This could be measured by placing her in a tank with marks on the side to measure how much water she displaces when floating and when held under water.) Round your answer to one decimal place.

ρ woman =____ kg/m3

What percent of her volume is above the surface when she floats in seawater (which as a density of 1025 kg/m3)? Round your answer to two decimal places.

Percentage above = ____%

A cyclist rides 6.2 km east, then 9.28 km in a direction 27.27 degrees west of north, then 7.99 km west.

A. What is the magnitude of the total displacement, in km?

B. What is the direction of the displacement, measured in degrees west of north?

A 3.0 m length of wire is made by welding the end of a 100 cm long silver wire to the end of a 200 cm long copper wire . Each piece of wire is 0.80 mm in diameter. The wire is at room temperature, so the resistivities are as given in the table below. A potential difference of 5.0 V is maintained between the ends of the 3.0 m composite wire.

(a) What is the current in the copper section?. A

(b) What is the current in the silver section? A

(c) What is the magnitude of vector E in the copper? V/m

(d) What is the magnitude of vector E in the silver? V/m

(e) What is the potential difference between the ends of the sliver section of wire? V