The acceleration due to gravity on the Moon's surface is one-sixth that on Earth. An astronaut's life support backpack weighs 240 lb on Earth. What does it weigh on the Moon?
a. 40 lb
c. 80 lb
b. 120 lb
d. 240 lb
[Ques. 2] A karate master strikes a board with an initial velocity of 10.0 m/s, decreasing to 2.0 m/s as his hand passes through the board. If the time of contact with the board is 0.0020 s, and the mass of the coordinated hand and arm is 1.0 kg, what is the force exerted on the board?
a. 1000 N
c. 4000 N
b. 6000 N
d. 4500 N
[Ques. 3] A baseball batter hits an incoming 40 m/s fastball. The ball leaves the bat at 60 m/s after a ball-on-bat contact time of 0.030 s. What is the force exerted on the 0.15 kg baseball?
a. 450 N
c. 90 N
b. 250 N
d. 500 N
[Ques. 4] A shot-putter moves his arm and the 7.0-kg shot through a distance of 1.0 m, giving the shot a velocity of 15 m/s from rest. Find the average force exerted on the shot during this time.
a. 197 N
c. 600 N
b. 394 N
d. 790 N
[Ques. 5] An automobile of mass 2000 kg moving at 20 m/s is braked suddenly with a constant braking force of 10,000 N. How far does the car travel before stopping?
a. 40 m
c. 120 m
b. 80 m
d. 160 m
[Ques. 6] A barefoot field-goal kicker imparts a speed of 30 m/s to a football at rest. If the football has a mass of 0.50 kg and time of contact with the football is 0.020 s, what is the force exerted on the foot?
a. 190 N
c. 600 N
b. 380 N
d. 750 N
[Ques. 7] Rita accelerates a 0.40-kg ball from rest to 12 m/s during the 0.15 s in which her foot is in contact with the ball. What average force does she apply to the ball during the kick?
a. 48 N
c. 24 N
b. 32 N
d. 64 N
[Ques. 8] A rock is rolled in the sand. It starts at 5.0 m/s, moves in a straight line for a distance of 6.0 m, and then stops. What is the magnitude of the average acceleration?
a. 2.1 m/s2
c. 5.4 m/s2
b. 4.2 m/s2
d. 6.2 m/s2
[Ques. 9] If the displacement of an object is given in SI units by Dx = -5t + t 2, at t = 2 s its velocity and acceleration are, respectively: (Hint: Use dimensional analysis along with the equations for motion with constant acceleration.)
a. positive, positive.
c. negative, negative.
b. positive, negative.
d. negative, positive.
[Ques. 10] A Cessna aircraft has a liftoff speed of 120 km/hr. What minimum constant acceleration does this require if the aircraft is to be airborne after a takeoff run of 200 m?
a. 2.31 m/s2
c. 4.63 m/s2
b. 2.78 m/s2
d. 5.55 m/s2
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