Q: How many joules of energy does a $$100-$$watt light bulb use per hour?

$$3.6 \times 10^5$\ \mathrm{J}$$

Question 1

A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface. The 6.00-kg block is pushed by a horizontal 10.0-N force. What is the magnitude of the force that the 6.00-kg block exerts on the 4.00-kg block?

Accepted Answer

$$6.00\ \mathrm{N}$$

Question 2

A car traveling at $$28.7\ \mathrm{m/s}$$ locks its brakes on dry pavement ($$\mu_k = 0.80). $$What is the minimum stopping distance?

Accepted Answer

$$52.5\ \mathrm{m}$$

Question 3

If the coefficient of kinetic friction between tires and wet pavement is $$0.25$$, what is the maximum speed you should drive to stop in the same distance as on dry pavement ($$52.5\ \mathrm{m}$$)?

Accepted Answer

$$16\ \mathrm{m/s}$$

Question 4

A person rides in an elevator while standing on a scale. The scale reads $$700\ \mathrm{N}$$, but the person’s actual weight is $$600\ \mathrm{N}. $$What is the acceleration of the elevator?

Accepted Answer

$$1.7\ \mathrm{m/s^2$}$$\ upward

Question 5

A series of weights connected by very light cords are given an upward acceleration by a pull $$P. $$The total mass is $$50.0\ \mathrm{kg}$$ and the acceleration is $$3.8\ \mathrm{m/s^2$}. $$What is the value of $$P$$?

Accepted Answer

$$690\ \mathrm{N}$$

Question 6

A $$2.00\ \mathrm{kg}$$ watermelon is dropped from rest from the roof of an $$18.0\ \mathrm{m}-$$tall building. Neglecting air resistance, what is the work done by gravity during its displacement?

Accepted Answer

$$353.0\ \mathrm{J}$$

Question 7

A farmer pushes a sheep of mass $$16.8\ \mathrm{kg} on a $$horizontal surface at a constant speed of $$3.50\ \mathrm{m/s}. $$The coefficient of kinetic friction is $$0.20. $$What horizontal force must the farmer apply?

Accepted Answer

$$33.0\ \mathrm{N}$$

Question 8

Superman throws a boulder of weight $$1850\ \mathrm{N} on $$Earth ($$g = 9.80\ \mathrm{m/s^2$}). $$What horizontal force must he apply to give it a horizontal acceleration of $$11.3\ \mathrm{m/s^2$}$$?

Accepted Answer

$$2130\ \mathrm{N}$$

Question 9

How many joules of energy does a $$100-$$watt light bulb use per hour?

Accepted Answer

$$3.6 	imes 10^5$\ \mathrm{J}$$

Question 10

In a perfectly ELASTIC collision between two perfectly rigid objects, which of the following is true?

Accepted Answer

Both the momentum and the kinetic energy of the system are conserved.

Question 11

Which free-body diagram best represents a person in an elevator traveling upward but slowing down at $$9\ \mathrm{m/s^2$}$$? $$F_t is $$the force of the floor on the person and $$F_g is $$the force of gravity.

Accepted Answer

$$F_t is $$less than $$F_g$$, both vertical and opposite directions.

Question 12

A spring with spring constant $$k = 250\ \mathrm{N/m} is $$stretched $$0.40\ \mathrm{m}$$ from equilibrium. What is the work done on the spring?

Accepted Answer

$$20.0\ \mathrm{J}$$

Question 13

A $$2.0\ \mathrm{kg}$$ object moves at $$5.0\ \mathrm{m/s}. $$What is its kinetic energy?

Accepted Answer

$$25.0\ \mathrm{J}$$

Question 14

A $$3.0\ \mathrm{kg}$$ object is moving at $$4.0\ \mathrm{m/s}. $$What is its momentum?

Accepted Answer

$$12.0\ \mathrm{kg\cdot m/s}$$

Question 15

A $$5.0\ \mathrm{kg}$$ object is acted on by a $$20.0\ \mathrm{N}$$ force for $$3.0\ \mathrm{s}. $$What is its final velocity if it starts from rest?

Accepted Answer

$$12.0\ \mathrm{m/s}$$

Question 16

A $$10.0\ \mathrm{kg}$$ box is pulled across a horizontal surface with a coefficient of kinetic friction $$\mu_k = 0.30. $$What is the frictional force?

Accepted Answer

$$29.4\ \mathrm{N}$$

Question 17

A $$2.0\ \mathrm{kg}$$ object is dropped from a height of $$10.0\ \mathrm{m}. $$What is its velocity just before hitting the ground? (Neglect air resistance)

Accepted Answer

$$14.0\ \mathrm{m/s}$$

Question 18

A $$1.5\ \mathrm{kg}$$ object is moving at $$2.0\ \mathrm{m/s}$$ and is stopped by a constant force over $$3.0\ \mathrm{m}. $$What is the magnitude of the force?

Accepted Answer

$$1.0\ \mathrm{N}$$

Question 19

A $$0.50\ \mathrm{kg}$$ ball is thrown vertically upward with an initial velocity of $$8.0\ \mathrm{m/s}. $$What is the maximum height reached?

Accepted Answer

$$3.3\ \mathrm{m}$$

PHY 2048: General Physics I – Kinematics, Dynamics, Work, Energy, and Collisions

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