Unit 7 review

What happens if you roll a ball at constant velocity off a friction-less table?

it covers equal distances in equal time intervals.

What is the approximate horizontal velocity at which the boy in the diagram threw the ball? Answer Choices: +25 m/s +30 m/s +5 m/s +20 m/s

Answer- +25 m/s

What is the spring constant for the spring in the graph? Answer Choices: +25.0 N/m -0.04 N/m -25.0 N/m +0.04 N/m

Answer- +25.0 N/m

projectile

an object that is propelled by a one-time force and acted on by independent horizontal and vertical forces

In the figure, a washer rotates on a string (string not shown) in the circular path shown in red. Which arrow best describes the velocity vector at that instant in time?

arrow B

What causes the centripetal acceleration of an electron in a hydrogen atom?

electrical attraction

Galileo was the first to realize that the motions of projectiles in the horizontal and vertical directions were ___________.

independent

trajectory

the path of any projectile

Which of the following is not in uniform circular motion?

orbiting satellite that speeds up near the earth and slows down far away

Which of the following is an example of projectile motion? Answer Choices: A bowler rolling her ball down an alley. A football in flight during a field goal. A child tumbling down a hillside A surfer riding a wave.

Answer- A football in flight during a field goal.

In the figure, which arrow represents the amplitude of the pendulum's motion? Answer Choices: arrow C arrow B arrow D arrow A

Answer- Arrow D

Which object moves in simple harmonic motion? Answer Choices: Moving car. Stretched rubber band with an attached mass. Orbiting satellite. Rolling ball going down a hill.

Answer- Stretched rubber band with an attached mass.

In the graph, why is the velocity positive at time 0.0 s? Answer Choices: The mass is moving downward and at the origin at 0.0 s. The mass is moving upward and at the origin at 0.0 s. The mass is moving upward but not at the origin at 0.0 s. The mass is moving downward but not at the origin at 0.0 s.

Answer- The mass is moving upward and at the origin at 0.0 s.

For the seesaw depicted in the diagram, which of the following will happen? Assume all the mass is distributed at the end of the seesaw arm and that the mass of the seesaw itself is negligible. Answer Choices: The seesaw will rotate counter-clockwise. You cannot tell from the information provided. The seesaw will remain balanced. The seesaw will rotate clockwise.

Answer- The seesaw will remain balanced.

Which statement explains how brakes slow down a car? Answer Choices: They apply a torque opposite the direction of motion. They apply a torque in the direction of motion. They apply an angular acceleration in the direction of motion. They apply an angular acceleration opposite the direction of motion.

Answer- They apply a torque opposite the direction of motion.

A soccer player kicks a soccer ball at +10.0 m/s at an angle of 60°. What are the horizontal and vertical components of velocity of the kick? Answer Choices: vx = -5.00 m/s and vy = +8.66 m/s v x = +5.00 m/s and v y = +8.66 m/s vx = -8.66 m/s and vy = +5.00 m/s v x = +8.66 m/s and v y = +5.00 m/s

Answer- v x = +5.00 m/s and v y = +8.66 m/s

A 1.00 m long pendulum in simple harmonic motion sits on the surface of Mars. It has a period of 3.26 s. What is the acceleration due to gravity on Mars?

3.71 m/s 2

A runner moving at a speed of 10.0 m/s rounds a bend with a 25.0 m radius. What is the centripetal acceleration that she experiences?

4.00 m/s2

Which of the following terms might a jet pilot use to describe a force that presses him against his seat during a high-speed turn?

centrifugal force

When you fling an object in the air or shoot it out of a cannon, it undergoes ____________.

projectile motion

How do you find the time and distance downrange of a horizontally fired projectile?

v(xcomponent)=vcos(0 degrees)=v(1)=v

Vertical distance equation at any time

y=v(down)yt+1/2gt(up)2

A pendulum has a period of 1.6 s. GIven: T=2 (Pie) {Sq rt.} L/g

0.64 m

The length of a pendulum in simple harmonic motion is 36 m. Given: T=2(Pie) (Sq.rt.) L/g

12 s

You apply 2.0 N of force to turn a 0.20 m long wrench clockwise on a pipe fitting. What is the torque that you apply? Answer Choices: 10.0 N/m clockwise 0.40 N • m clockwise 0.40 N clockwise 10.0 N clockwise

Answer- 0.40 N • m clockwise

Who invented the first pendulum clock? Answer Choices: Galileo Huygens Foucault Harrison

Answer- Huygens

Why do projectiles follow curved paths?

If a ball rolls off a table it would move the same horizontal distance, but the vertical distance would increase as the square of time. since it is a combination of two different and independent motions of the object.

Horizontal distance equation

x=v(down)xt

What did Galileo conclude

-Objects fell at the same rate regardless of mass. -If an object was at rest it would remain at rest. If it was in motion at constant velocity in a straight line, it would remain in that motion unless an outside force acted on it. (Galileo's findings on inertia were later restated by Newton as his first law of motion.) -Objects undergoing constant acceleration (or free fall) could be described by the kinematic equations.

A 70.0 kg runner moving at a speed of 10.0 m/s rounds a bend with a 25.0 m radius. What is the centripetal force that she experiences?

280 N

A point on the tread of a tire with a radius of 0.50 m rotates one-quarter turn, which is π/2 radians. What is the linear distance of the displacement? Answer Choices: 0.32 m 1.6 m 0.45 m 0.79 m

Answer- 0.79 m

For the figure, during what time interval does vy become zero? Answer Choices: never. 2-3 s. 0-1 s. 1-2 s.

Answer- 1-2 s.

A ball moving at +3.0 m/s along a table rolls off a table and lands on the ground 2.0 m away. How high was the table? Answer Choices: 2.2 m 3.0 m 1.1 m 3.3 m

Answer- 2.2 m

If you exert 10.0 N of force to compress a spring 50 cm from its equilibrium point, then what is the spring constant? Be sure to convert to meters. Answer Choices: 30 N/m 20 N/m 10 N/m 40 N/m

Answer- 20 N/m

A golfer hits a golf ball with a club head angled at 30°. He swings with a velocity of +50.0 m/s. How far will the ball travel horizontally? Answer Choices: 130 m 160 m 220 m 50 m

Answer- 220 m

Calculate the torque produced by a force of 50.0 N applied clockwise perpendicular to the end of a bar of length 0.50 m. Answer Choices: 10 N • m clockwise 25 N • m clockwise 100 N/m clockwise 45 N • m clockwise

Answer- 25 N • m clockwise

What is the period of the spring's motion in the position-time graph shown here? Answer Choices: 1.0 s 2.0 s 3.0 s 1.5 s

Answer- 3.0 s

Which of the following springs (described by its spring constant) has the shortest period when attached to a 100 g mass? Answer Choices: 30.0 N/m. 10.0 N/m. 20.0 N/m. 40.0 N/m.

Answer- 40.0 N/m

The crankshaft of an engine increases its spin from 1,200 rpm to 1,500 rpm in 0.50 s. What is its angular acceleration? Answer Choices: 300 rad/s 2 63 rad/s 2 10 rad/s 2 600 rad/s 2

Answer- 63 rad/s 2

A boy throws a stone with a velocity of +20.0 m/s at an angle of 30°. How long does it take the stone to hit the ground? How far will the stone have traveled when it hits the ground? How high will it go?

Given: v = +20.0 m/s, θ = 30° ,g = −9.8 m/s2 The reference is (0, 0) at the ground, so the sign of g is negative, since g is acting toward the reference point. Unknown: t=?, range(xmax) = ?, altitude(ymax) = ? Equation: