Download Ch 4 Review Worksheet

Physics Review – Ch 4
Name ______________________________
1) Is it possible to have motion in the absence of a force? Explain.
2) If an object is at rest, can we conclude that no external forces are acting on it?
3) An object thrown into the air stops at the highest point in its path. Is it in equilibrium at this point?
Explain.
4) State Newton’s first law.
5) What physical quantity is a measure of the amount of inertia an object has?
6) A large crate is placed on the bed of a truck but not tied down.
a) As the truck accelerates forward, the crate slides across the bed until it hits the tailgate. Explain what
causes this.
b) If the driver slammed on the brakes, what would happen to the crate?
10)Four forces act on a hot-air balloon, shown in Figure 4-29 on pg151 of your text. Find the magnitude
and the direction of the resultant force on the balloon.
11) Two lifeguards pull on ropes attached to a raft. If they pull in the same direction, the raft experiences a
net external force of 334N to the right. If they pull in opposite directions, the raft experiences a net
external force of 105N to the left.
a) Draw a free-body diagram representing the raft for each situation.
b) Find the force exerted by each lifeguard on the raft.
13) Earth is attracted to an object with a force equal to and opposite the force Earth exerts on the object.
Explain why Earth’s acceleration is not equal to and opposite that of the object.
14) Explain Newton’s second law in terms of inertia.
19) Explain why a rope climber must pull downward on the rope in order to move upward.
21) What acceleration will you give to a 24.3 kg box if you push it with a force of 85.5N? (Assume no
friction)
23) A freight train has a mass of 1.5 x 10 7 kg. If the locomotive can exert a constant pull of 7.5 x 10 5N,
how long would it take to increase the speed of the train from rest to 85 km/hr?
25) A boat moves through the water with two forces acting on it. One is a 2.10 X 10 3 N forward push by
the motor and the other is a 1.80 x 103 N resistive force due to the water.
a) What is the acceleration of the 1200 kg boat?
b) If it starts from rest, how far will it move in 10.0s?
c) What will its velocity be at the end of this time interval?
26) Two forces are applied to a car in an effort to accelerate it, as shown in Figure 4-30.
a) What is the resultant of these 2 forces?
b) If the car has a mass of 3200kg, what acceleration does it have? Disregard friction.
29) A 2.0 kg mass starts from rest and slides down an inclined plane 0.80m long in 0.50s. What net force is
acting on the mass along the incline?
34) Explain the relationship between mass and weight.
35) A 0.150 kg baseball is thrown upward with an initial speed of 20.0 m/s.
a) What is the force on the ball when it reaches half its maximum height?
b) What is the force on the ball when it reaches its peak?
36) Draw a force diagram showing the weight and normal forces on a laundry basket in each of the
following situations:
a) at rest on a horizontal surface
c) at rest on a ramp inclined 25º above the horizontal.
37) If the basket in item 36 has a mass of 5.5 kg, find the magnitude of the normal force
a) for the situation in 36a.
b) for the situation in 36c.
39) A massive metal object on a rough metal surface may undergo contact welding to that surface. Discuss
how this affects the frictional forces that arise between object and surface.
45) A loaf of bread weight 5.30N on Earth.
a) What should it weigh, in newtons, on the moon, where the acceleration due to gravity is one-sixth that on
Earth?
b) What should it weigh, in newtons, on the Jupiter, where g is 2.64 times Earth’s gravity?
47) A 3.46 kg briefcase is sitting at rest on a level floor.
a) What is it’s acceleration?
b) What is it’s weight in newtons?
49) A 5.4 kg bag of groceries is in equilibrium on an incline of angle 15º. Find the normal force of the
incline on the bag.
50) Find the force exerted by each cable to support the 625 N bag in Figure 4-32 on pg 154 of your text.
55) A clerk moves a box of cans down an aisle by pulling on a rope attached to the box. The clerk pulls
with a force of 185 N at an angle of 25º with the horizontal. The box has a mass of 35.0 kg, and the
coefficient of kinetic friction between box and floor is 0.450. Find the acceleration of the box.
61) The coefficient of static friction between the 3.00 kg crate and the 35º incline of Figure 4-34 is 0.300.
What is the minimum force, F, that must be applied to the crate perpendicular to the incline to prevent the
crate from sliding down the incline?