Q: Given the vectors $$\vec{A}$$ and $$\vec{B}$$ shown in the first image, which of the following correctly expresses the dot product $$\vec{A} \cdot \vec{B}$$?

$$|\vec{A}| |\vec{B}| \cos \theta$$

Q: A 1.00 kg basketball is thrown straight up with an initial speed of 6.50 m/s from a height of 1.80 m. What is the maximum height (above the ground) the ball reaches? (Neglect air resistance, $$g = 9.8\ \mathrm{m/s^2$})$$

$$1.80\ \mathrm{m} + \frac{(6.50)^2$}{2 \times 9.8}$$

Question 1

Given the vectors $$\vec{A}$$ and $$\vec{B}$$ shown in the first image, which of the following correctly expresses the dot product $$\vec{A} \cdot \vec{B}$$?

Accepted Answer

$$|\vec{A}| |\vec{B}| \cos 	heta$$

Question 2

A box is being pushed in the negative x-direction on a horizontal floor, as shown in the second image. What is the work done by the normal force on the box?

Accepted Answer

Zero

Question 3

A 1.00 kg basketball is thrown straight up with an initial speed of 6.50 m/s from a height of 1.80 m. What is the maximum height (above the ground) the ball reaches? (Neglect air resistance, $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$1.80\ \mathrm{m} + \frac{(6.50)^2$}{2 	imes 9.8}$$

Question 4

What is the value of the gravitational potential energy at the maximum height for the basketball in the previous question? (Let $$U = 0 at $$ground level)

Accepted Answer

$$mgh_{max}$$

Question 5

A 5000-kg freight car moving on frictionless rails compresses a spring by 0.46 m before coming to rest, as shown in the third image. The spring constant is $$46,000\ \mathrm{N/m}. $$What is the potential energy stored in the spring at maximum compression?

Accepted Answer

$$\frac{1}{2} k x^2$

Question 6

What was the initial kinetic energy of the freight car before it hit the spring?

Accepted Answer

$$\frac{1}{2} k x^2$

Question 7

A boy pulls his sister in a wagon (see fourth image) with a force $$F = 40.5\ \mathrm{N} at an $$angle of $$30^\circ$$ above the horizontal for a distance of $$1.475\ \mathrm{m}. $$What is the work done by the boy?

Accepted Answer

$$F d \cos 	heta$$

Question 8

If the boy in the previous question pulls the wagon for 1 minute, what is his average power output?

Accepted Answer

$$\frac{W}{t}$$

Question 9

A 62.5 kg skater moving at 4.75 m/s collides with a stationary 75.0 kg skater. After the collision, they move together. What type of collision is this?

Accepted Answer

Perfectly inelastic

Question 10

What is the magnitude of the initial momentum of the 62.5 kg skater before the collision?

Accepted Answer

$$m v$$

Question 11

After the collision described above, what is the final speed of both skaters together?

Accepted Answer

$$\frac{m_1$ v_1$}{m_1$ + m_2$}$$

Question 12

A car of mass 65.0 kg crashes into a tree and stops in 0.24 s from an initial speed of 5.50 m/s. What is the change in momentum of the driver?

Accepted Answer

$$m (v_f - v_i)$$

Question 13

What is the magnitude of the impulse delivered to the driver by the seatbelt during the collision?

Accepted Answer

$$|\Delta p|$$

Question 14

What is the magnitude of the average force exerted by the seatbelt on the driver to bring her to a halt?

Accepted Answer

$$\frac{|\Delta p|}{\Delta t}$$

Question 15

Is it possible for a system to have negative potential energy?

Accepted Answer

Yes

Question 16

An elevator is moving upwards. What is the work done by gravity on the elevator?

Accepted Answer

Negative

Question 17

Which of the following statements is correct regarding the unit 'Watt'?

Accepted Answer

Watt is the unit of power

Physics I: Work, Energy, Momentum, and Collisions – Guided Study Notes

Study Guide - Practice Questions

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