Grade 12Mechanics
1. The position of a 2.75⋅105 N training helicopter under test is given by r = (0.020 m/s3 )t3 I
+ (2.2m/s)t j - (0.060m/s2 )t2 k. Find the net force on the helicopter at t = 5.0 s.
2. A stockroom worker pushes a box with mass 11.2 kg on a horizontal surface with a constant speed of 3.50
m/s. The coefficient of kinetic friction between the box and the surface is 0.20. (a) What horizontal force
must the worker apply to maintain the motion? (b) If the force calculated in part (a) is removed, how far does
the box slide before coming to rest?
1. The position of a 2.75⋅105 N training helicopter under test is given by r = (0.020 m/s3 )t3 I
+ (2.2m/s)t j - (0.060m/s2 )t2 k. Find the net force on the helicopter at t = 5.0 s.
2. A stockroom worker pushes a box with mass 11.2 kg on a horizontal surface with a constant speed of 3.50
m/s. The coefficient of kinetic friction between the box and the surface is 0.20. (a) What horizontal force
must the worker apply to maintain the motion? (b) If the force calculated in part (a) is removed, how far does
the box slide before coming to rest?
