Physics 111 HW16
assigned 30 March 2011
J01. A spring pushes a 2kg mass on a level frictionless table. The mass starts at rest and
when it leaves the spring 5 seconds later it is going 3 m/s.
a) Find the impulse delivered to the mass.
b) Find the average force on the mass during the time it pushes the mass.
J02. A baseball has a mass 0.145 kg.
a) If the velocity of a pitched ball has a magnitude of 45.0 m/s and the batted ball’s
velocity is 55.0 m/s in the opposite direction, find the magnitude of the change in
momentum of the ball (the impulse) applied to it by the bat.
b) If the ball remains in contact with the bat for 2.00 ms, find the magnitude of the
average force applied by the bat.
J03. An engine of the orbital maneuvering system (OMS) on a space shuttle exerts a
force of (26,700 N)ĵ for 3.90s, exhausting a negligible mass of fuel relative to the
95,000-kg mass of the shuttle.
a) What is the impulse of the force for this 3.90 s?
b) What is the shuttle’s change in momentum from this?
c) What is the shuttle’s change in velocity from this?
d) Why can’t we find the resulting change in kinetic energy of the shuttle?
J05. A soldier on the firing range fires burst from a .50 M2 Browning machine gun at a
full automatic rate of 20 rounds per second. Each bullet has a mass of 160 g and a
speed of 900 m/s relative to the ground as it leaves the barrel of the weapon.
Calculate the average recoil force exerted on the weapon during that burst.
J06. A bouncy ball is dropped from a height of ho (close to the surface of the Earth) and
bounces back up to a height h1. Derive an expression for the magnitude of the
average force delivered to the ball by the ground when it bounces in terms of the time
of contact t, the mass of the ball m, ho, h1, and fundamental constants.
J07. A soccer ball goes east at 5 m/s when it is kicked by a soccer player. After the kick,
it is going NW at 15 m/s. If the ball is in contact with the player’s foot for 0.08
seconds, calculate the average force (magnitude and direction) the player delivers to
the ball during the kick.