Q: A skier of mass 66 kg is moving down a frictionless slope inclined at $$22^{\circ} to $$the horizontal. What is the magnitude of the component of the skier's weight parallel to the slope?

$$66 \times 9.8 \times \sin(22$$^{\circ}$$) = 246 N$$

Q: A 1200 kg car accelerates from rest to $$27.0 m/s in$$ $$10.0 s. $$What is the average net force required?

$$F = m \frac{\Delta v}{\Delta t} = 1200 \times \frac{27.0}{10.0} = 3240 N$$

Q: A 15.0-kg crate sits on a flatbed truck. If the coefficient of static friction between the crate and the truck is $$0.380$$, what is the maximum acceleration the truck can have before the crate starts to slide?

$$a_{max} = \mu_s g = 0.380 \times 9.8 = 3.73 m/s$^2$$

Q: A car travels at $$23 m/s $$around a circle. If the coefficient of static friction between the tires and the road is $$0.44$$, what is the maximum radius of the circle the car can travel without skidding?

$$r_{max} = \frac{v^2$}{\mu_s g} = \frac{(23)^2$}{0.44 \times 9.8} = 123 m$$

Q: A 1600 kg SUV slows from $$42.0 m/s to$$ $$17.0 m/s. $$How much work is done on the SUV?

$$W = \frac{1}{2} m (v_f^2$ - v_i^2$) = \frac{1}{2} \times 1600 \times (17^2$ - 42^2$) = -1.18 \times 10^6$ J

Q: An object of mass $$20 kg is $$lifted vertically through $$1.00 m by a$$ $$396 N $$force. What is the net work done?

$$W_{net} = F_{net} \times d = (396 - 20 \times 9.8) \times 1 = 200 J$$

Q: A 3.4 kg object is held at the top of a triangular wedge (height $$3 m). $$What is its gravitational potential energy relative to the base?

$$U = mgh = 3.4 \times 9.8 \times 3 = 233 J$$

Q: An object of mass $$4.00 kg $$sits at the top of a frictionless inclined plane of height $$18 m. $$What is its speed right before it reaches the bottom?

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 18} = 19 m/s$$

Question 1

A skier of mass 66 kg is moving down a frictionless slope inclined at $$22^{\circ} to $$the horizontal. What is the magnitude of the component of the skier's weight parallel to the slope?

Accepted Answer

$$66 	imes 9.8 	imes \sin(22$$^{\circ}$$) = 246 N$$

Question 2

A 1200 kg car accelerates from rest to $$27.0 m/s in$$ $$10.0 s. $$What is the average net force required?

Accepted Answer

$$F = m \frac{\Delta v}{\Delta t} = 1200 	imes \frac{27.0}{10.0} = 3240 N$$

Question 3

A 15.0-kg crate sits on a flatbed truck. If the coefficient of static friction between the crate and the truck is $$0.380$$, what is the maximum acceleration the truck can have before the crate starts to slide?

Accepted Answer

$$a_{max} = \mu_s g = 0.380 	imes 9.8 = 3.73 m/s$^2$$

Question 4

A 3-kg ball moves in a horizontal circle of radius $$0.3 m at a $$constant speed of $$27 cm/s. $$What is the ball's acceleration?

Accepted Answer

$$a = \frac{v^2$}{r} = \frac{(0.27)^2$}{0.3} = 0.24 m/s$^2$$

Question 5

A car travels at $$23 m/s $$around a circle. If the coefficient of static friction between the tires and the road is $$0.44$$, what is the maximum radius of the circle the car can travel without skidding?

Accepted Answer

$$r_{max} = \frac{v^2$}{\mu_s g} = \frac{(23)^2$}{0.44 	imes 9.8} = 123 m$$

Question 6

A 1600 kg SUV slows from $$42.0 m/s to$$ $$17.0 m/s. $$How much work is done on the SUV?

Accepted Answer

$$W = \frac{1}{2} m (v_f^2$ - v_i^2$) = \frac{1}{2} 	imes 1600 	imes (17^2$ - 42^2$) = -1.18 	imes 10^6$ J

Question 7

An object of mass $$20 kg is $$lifted vertically through $$1.00 m by a$$ $$396 N $$force. What is the net work done?

Accepted Answer

$$W_{net} = F_{net} 	imes d = (396 - 20 	imes 9.8) 	imes 1 = 200 J$$

Question 8

A 3.4 kg object is held at the top of a triangular wedge (height $$3 m). $$What is its gravitational potential energy relative to the base?

Accepted Answer

$$U = mgh = 3.4 	imes 9.8 	imes 3 = 233 J$$

Question 9

An object of mass $$4.00 kg $$sits at the top of a frictionless inclined plane of height $$18 m. $$What is its speed right before it reaches the bottom?

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 18} = 19 m/s$$

Question 10

A 2.00-g bullet traveling at $$700 m/s $$embeds in a stationary $$5.00-kg $$wood block. What is the speed of the block immediately after?

Accepted Answer

$$v = \frac{m_{bullet} v_{bullet}}{m_{bullet} + m_{block}} = \frac{0.002 	imes 700}{0.002 + 5} = 0.28 m/s$$

Question 11

A batter applies an average force of $$8000 N to a $$baseball for $$1.10 ms. $$What is the magnitude of the impulse delivered?

Accepted Answer

$$J = F \Delta t = 8000 	imes 0.0011 = 8.8 N$\cdots$$

Question 12

A 3.0-kg object moves right at $$4.0 m/s $$and collides head-on with a 6.0-kg object moving left at $$2.0 m/s. $$What is the total momentum before the collision?

Accepted Answer

$$p_{total} = 3.0 	imes 4.0 + 6.0 	imes (-2.0) = 12 - 12 = 0 kg$\cdotm/s$$

Question 13

A skier is moving down a frictionless slope inclined at $$22^{\circ}. $$Which force is responsible for the skier's acceleration down the slope?

Accepted Answer

The component of gravity parallel to the slope: $$mg \sin(22$$^{\circ}$$)$$

Question 14

A block of mass $$m$$ rests on an inclined plane of angle $$	heta. If $$the angle is increased, what happens to the normal force?

Accepted Answer

It decreases: $$N = mg \cos 	heta$$

Question 15

A ball is thrown upward. Ignoring air resistance, what is the net force acting on it at half its maximum height?

Accepted Answer

Equal to its weight: $$F_{net} = mg$$

Question 16

For uniform circular motion, what is the relationship between the velocity and acceleration vectors?

Accepted Answer

They are perpendicular to each other at every point on the circle

Question 17

If the net work done on an object is negative, what happens to its kinetic energy?

Accepted Answer

It decreases

Question 18

An acorn falls from a tree. How do its kinetic energy $$K$$ and potential energy $$U$$ change as it falls?

Accepted Answer

$$K$$ increases and $$U$$ decreases

Physics 1230G Practice Exam 2 – Step-by-Step Study Guidance

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