Mechanics | Relativity Answers

Student drops a ball from a building and it takes 3 seconds to reach the ground. What was its speed before hitting the ground?

Hilda Spellman was baking a pie for Sabrina’s 16th birthday, when the dough won’t roll flat on the kitchen table. She hit the 20 cm dough flat using a spatula moving at a velocity of 30 m/s downward, until the dough is 5 mm thick. The dough remained immobile throughout the process.

1. If the spring constant of the dough is equal to 50, what is the momentum of the dough?
2. What kind of collision is observed in the scenario?

A mass of 0.750 kg is hung from a vertical spring with a spring constant of 20 N/m. After coming to equilibrium the mass is then pulled down an additional distance 10 cm and then released from rest. The mass then oscillates from position 3 to 4 to 5 to 4 and back to 3 over and over.

A) List the types of nonzero energy that the system has at xmin (Position 5). B) Calculate xeq.

C) Calculate hmax.

D) Calculate the total energy of the system at xmax (Position 3).

E) Calculate the maximum speed.

F) Calculate the amounts of EK, Eg, and ES when the mass is 4.00 cm above the equilibrium position.

G) Explain two ways that the maximum speed can be decreased

A foam cup is filled with a hot water and allowed to cool while being stirred by a paddlewheel.

initially, the water has an internal energy of 200kj,and while cooling it loses 150kj of heat.

the paddlewheel does 25kj of work on water

a) calculate the change in internal energy of water

b) calculate the final internal energy of water

A wave out in the deep ocean has an amplitude of 1.51 m, a wavelength of 212 m and a period of 14.3 s

What is the speed of such a wave? (in m s⁻¹ to 3 s.f)

A small toy gun fires light foam projectiles by compressing a spring. As the spring relaxes it pushes the projectile.

The toy gun has a spring with a spring constant of 484 N m−1, the spring is compressed by 5.00 cm, and it fires a 10.0 g projectile.

At what speed does the projectile leave the toy gun? (in m s−1 to 3 s.f)

A runaway 185 kg wheeled skip is rolling east along a road with a velocity of +2.2 m s−1. A 2560 kg car moving to the west with a velocity of −9.7 m s−1 hits the skip.

After the collision the skip is moving west with a velocity of −14.4 m s−1.

What is the velocity of the car after the collision? (in m s−1 to 2 s.f)

A person throws a 755 g ball up at an angle such that it has an initial speed of 15.0 m s−1. After a short time the ball has a speed of 5.30 m s−1.

How much higher is the ball than when it was let go? (in m to 3 s.f)

(note: use g = 9.81 m s−2)

A person is riding in a car which is moving at a constant speed around a circular arc.

The person has an accelerometer on their mobile phone and uses it to measure a lateral (horizontal) acceleration of 5.6 m s−2.

If the car was traveling at 50 km h−1 (14 m s−1) then what was the radius of the curve that car was traveling along? (to 2 s.f)

A 64.0 kg person is riding an elevator as shown in the figure above. The elevator is accelerating upwards at a rate of 0.682 m s−2.

For this problem use g = 9.81 m s−2

What is the magnitude of the normal force, the force on the person from the elevator? (in N to 3.s.f)